Wednesday, 31 October 2018

A History of RAF Skaw (AMES 56) - Post War Skaw

RAF Skaw did not close immediately after VE Day (Monday 8 May 45), ships were still at sea, Coastal Command had ongoing operations and there was the remote possibility that some German aircrew would not accept that the war was over. VJ Day, 15 Aug 45, marked the end of the war in Far East. The Skaw Chain Home Station actually ceased reporting on 4 Aug 45 and was placed on care and maintenance with effect from the 22nd - two weeks later. However, some classified experimental work kept some of the equipment operational and a few dedicated personnel on site for a period after this. The operational history notes that in Oct 45 "Both Channels of the Type 1 AMES at SKAW (the Chain Home Radar) on a "caretaking basis" have been overhauled by a Wing party: authority had not been received as yet from HQ 60 Group to lower the Transmitter curtain arrays" Then there is an entry on 21 Nov, which says: "Type 1 Skaw: Gave instructions for this Station to become operational for the limited purposes of research on Air Ministry instructions".

Early in the New Year ('46) there are further entries: "The Type 1 at SKAW, although on a care and maintenance basis, has been carrying out transmissions for experiments in Porto Rico. The R.N.A. (Radio Navigation Aid) channel at SKAW has been placed on a caretaking basis, and it has been found impossible to carry on with experimental transmissions. Authority has been sought from HQ No. 60 Group to cease transmissions on the type 1" and, on 24 Feb 46 it is recorded that; "The experimental work being carried out at SKAW was discussed with M.3.  It was pointed out that this section was holding two mechanics at SKAW for this experimental work, and it was requested that information be obtained as to the probable duration of the experiment. M.3. pursued the matter with HG No. 60 Group, but since Air Ministry and WASHINGTON are involved, no immediate decision could be given". So far I have not been able to discover the nature of this "experimental work" with US. It may well be unrelated but, the Loran navigation site, AMES713 at Outer Skaw just north of RAF Skaw, closed down on 20 Feb 46 and was placed on care & maintenance.

At one stage the number of servicemen based in Shetland during WWII peaked at over 20,000. All of these men had to be fed, accommodated and transported.  As early as 1946, it was realised that it would not be economic to ship much of the less valuable material back to the UK mainland. In the next few years many items were sold off within Shetland and the opportunity for those civilians with a little capital to purchase items like nissen huts, wooden huts , barrack room furniture and some vehicles, existed. Unst with Skaw, the Navy radar on Saxa & the Home Guard would have had plenty of material for disposal. However, at the time when the Transmitter and Receiver towers were demolished in 1947, much of the Domestic Site was still standing. The following photo, taken from the top of one of the  360' Transmitter Towers, was sent to the late Lexie McMeechan by Leslie Smith:

The decision to dismantle the RAF Skaw Chain Home site (along with a number of others), was not long in coming. The Towers were blown up in 1947. The following photo from an Unst History Group Calendar shows the northerly 360' Transmitter Tower in the process of collapsing, with the hill of Saxa Vord in the left background:
Unfortunately this  tower landed on the roof of the uninhabited Transmitter Block, where it caused some damage, as can be seen in this picture from Leslie Smith:
Some of the damage is still visible 70 years later:

The 240' wooden Receiver Towers came down more successfully, but I have no idea what happened to the tons of Douglas Fir they had been constructed with - but I could make a few guesses, wood being a scarce commodity on Unst!

As can just be seen in the left  of  picture above, the 105' Mk3 IFF mast is still standing but it was probably lowered, using the cable guys, soon after.

After a short time the only structures left were those which had been built with concrete and bricks (Bunkers, Power House, Cook House, Air Raid Shelters, etc). During Aug 54 the land, which had been occupied by the Air Ministry for RAF Skaw,  it's Remote Reserve and subsequent Loran site, was derequisitioned (ie, returned to its previous owners).

Coincidentally, 1954 was when preparatory work on the construction of RAF Saxa , with its Power House and Bulk Fuel Installation, began.  Once again many workers from Shetland and the UK Mainland were needed for the projects and it is quite possible that many of the civilians who helped build the WWII sites in the Islands and some of the ex servicemen who worked on them were involved.

In the period since RAF Skaw closed the land the military occupied has seen many different activities.  Primarily the area has been returned to crofting use but many leisure pursuits have also taken place. For a number of years the personnel from RAF Saxa Vord had a self-maintained golf course, the Standby Power house has been used by local boat owners to provide shelter for maintenance work and for a while the galley for the Norwick Up Helly Aa was assembled in the building.

The headland at Inner Skaw has become a place for rock climbers to practise their hobby on its cliffs and, with its extreme north-easterly position, it makes an attractive landing point for rarer migratory birds which can attract many "twitchers". 
  With the discovery of North Sea Oil two new masts were erected for navigation/communication purposes. The first, and smaller of the two, was erected just to the south of the old CH Receiver Blocki. It was owned by Racal Survey Norway  and operated as part of a system called Deltafix, a photo from Mike Pennington is below:


The second structure  was a 300' guyed mast from Racal Survey and was part of the Pulse/8 system:

Both the Delafix and Pulse/8 systems were similar to an advanced form of Loran and, over shorter distances, enabled the crews of vessels involved in the North Sea Oilfields to fix their positions with great accuracy.
From the Mid 50's both the RAF and the Admiralty had personnel at Saxa. Unfortunately people generate rubbish and, in the days before the Council accepted responsibility for removing domestic waste from service establishments, much of it was disposed of at the site of RAF Skaw using 2 tipping points (use dependent upon wind direction and strength). It is possible that these two places were in use during WWII but I have no record of that. The first tipping point, to the south, was into an area called The Mooasunds and looked like this:
The second site was very close and to the north  of the headland, at a place called Gwykerls Geo:

The amount of debris which accumulated over the years, both from civilians and servicemen, was considerable and included numerous vehicles and much machinery!

Occasionally, when parts of RAF Saxa Vord were being refurbished, there would be an interchange of information between service employees and civilians. MOD would not allow used items to be given away, only sold by strictly supervised auctions - difficult to organise in Unst - or physically scrapped. It was not unknown at certain times for folk to be below the tipping points to see what  scrapped goodies would descend on them from above! Early in the 90's I think the Shetland Islands Council agreed to collect domestic waste from RAF Saxa Vord and, initially, this was taken to official landfill sites - although some people continued dumping at Skaw it could no longer be considered  "legal" to do so. There was a less well known third tipping site, possibly constructed for the Admiralty in the 50's, at Outer Skaw. This was used to dump material into Forn Geo.
Another activity in the 70's, which would be strongly discouraged nowadays, was the use of a structure built in 1940 as part of the RAF Skaw Advance Chain Home radar site, for fire practice. This was illustrated in the Saxa bog here:

The area suffered a setback in 1995 when the road to Skaw (The Floggie), had to be closed as unsafe. Large cracks had appeared and there was a great danger of the cliff side collapsing into the water below:

Eventually a new, much longer, road was built and it was possible to gain vehicular  access to Skaw by a route which avoided the cliffs altogether.
At the end of the 20th century an unsuccessful attempt was made to get money from the "Millennium Fund" to turn the old RAF Skaw Receiver Block into a safe visitor attraction, in the hope of generating tourist activity.  Those of you who believe in the preservation of historic sites will be pleased to know that in 2012 Historic Environment Scotland designated RAF Skaw, both main and reserve sites, a "scheduled monument" - the details of this decision may be seen here:
Previous articles on RAF Skaw
Part 1 of RAF Skaw - Inception to Jan '41 is here:

Part 2 of RAF Skaw - Advance CH - From Jan 41 to May 42s is here:

 Part 3 of RAF Skaw - CH Ops is here:
Part 5 of RAF Skaw - Some of the Other Buildings at RAF Skaw
Part 6 of RAf Skaw - Defence & Protection
Part  7 of A RAF Skaw - Remote Reserve AMES 56R
AVIA 7 - 312 Unst, The National Archive
Air 26 - 094 HQ 70 Wg ORB Appendices, The National Archive
AIR 26 - 095 HQ 70 Wg ORB, The National Archive
Air 26 - 100 HQ 71 Wg ORB, The National Archive
SD 0458 - Photographic Record of Radar Stations (Ground), Air Ministry, Aug 43
Mike Dean MBE
Leslie Smith
Gerry Firmin
Lexie McMeechan
Rita Carle


Sunday, 30 September 2018

A History of RAF Skaw ( AMES 56) Part 7 - Remote Reserve AMES 56R

The idea of back-up facilities for Chain Home Radar Stations originated early on in WWII. By the middle of Aug '40, at the height of the Battle of Britain and as a result of some success by the Luftwaffe, it was decided that radar sites in the SE, including Ventnor, Pevensey, Rye and Dover, needed better physical protection, better anti-aircraft protection, more back-up equipment and better dispersal of resources. This led to a number of measures which included hardened shelters, provision of mobile assets and the construction of "reserve sites". The static reserve sites fell into 2 categories, Buried Reserves and Remote Reserves. As the name suggests, Buried Reserves tended to be on or near the main site, with most of the equipment and personnel underground for protection - only the towers and aerial arrays were exposed. On the other hand, Remote Reserves were some distance from the main sites, usually above ground, with some degree of protection and usually camouflaged. The cost and complexity of building Buried Reserves meant that, for economic reasons, most back-up sites  after Spring 1941, especially those in the west and north, were built as Remote Reserves.
Although the two Shetland Chain Home Sites were not among the first to be built, the inclusion of Reserve Sites was agreed long before the full Chain Home Radar sites were complete. The Advance Chain Radars in Shetland were operational at the beginning of 1941 but the full Chain Home Radars were not commissioned until April & May '42. Discussion about the siting of their Reserves began as early as May '41. In this article I will be dealing with RAF Skaw, the story of RAF Noss Hill has been published elsewhere (

Finding a suitable location for the RAF Skaw Remote Reserve was not simple. Discovering a large enough piece of land with, all the right characteristics  and within a suitable distance of the main site proved to be a problem and, in the end, compromises were made. The Authorities were after a piece of land 500 to 2,000 yards from the main CH equipment and with good access. It had to provide maximum detection ranges on the 2 main Lines of Shoot - 100 degrees and 280 degrees. There needed to be as little distortion the radio signals as possible. At the beginning of Jun '41 it was decided that the best place available would be on the headland of Outer Skaw to the north of Lamba Ness (Inner Skaw)- Left Click on pictures to enlarge,
The selected position could to be used for height-finding but this facility would be restricted in the west where higher ground would cause problems. In July a number of details for the reserve were officially recorded. It would fall under the jurisdiction of HQ 71 Group, be under the command of RAF Skaw, have the name Skaw Remote Reserve and be allocated the designation "Air Ministry Experimental Station"(AMES) 56R, (RAF Skaw was AMES 56). The mean height was recorded as 63' and the exact position was noted using the wartime National Grid System. The lines of shoot for the radar were recorded as 010, 100, 190 and 280. The land at Outer Skaw was shown to belong to the Garth Estates Ltd and the tenant was a T. Clark Esq of the Haa, Skaw.

"Good access" was available by a track which ran from near the RAF Skaw main domestic site to the "Haa". The track was not built for heavy vehicles  and the surface deteriorated quickly when used by construction firms, especially in the winter months. Having got as far as the "Haa" the route had to be extended half a mile to the furthest point of the Reserve site (the Receiver Building). Construction would have been undertaken by a couple of the firms responsible for building the main CH Site on Lamba Ness - Riley & Neat & WJ Watsons,. The main structures on the Reserve were 2 wooden towers , a Receiver Hut, a Transmitter  Hut and a building to house the Generators . Other elements  of the site included  a Guard Post, a Mess Hall, 2 x Chemical WC cubicles and areas for disposal of rubbish. It was not the intention that the site be permanently manned by technicians and operators. If needed, crews would come from the off-duty personnel at the main site or from survivors of an attack. The only permanent manning was intended to be an Army guard, probably from the local defence forces already allocated to defend RAF Skaw.  The Flash Earth image below shows the approximate location  of the various parts of the Reserve - more details will follow shortly:

The Transmitter and Receiver Towers were both 120' tall and made of wood. They have long since been dismantled but similar towers, from St Lawrence on the Isle of Wight, can be seen in this photo from the Imperial War Museum:
A low quality plan of the 120' Towers is seen below:
 At the base the legs of each Tower formed a square, approximately 16' x 16'. What remains of the base of the Transmitter Tower can be seen in this recent photo:

The Towers were demolished in 1944 and  a Tower was subsequently rebuilt as part of the transmission system for the AMES713 LORAN Unit . This was where the old Receiver Tower used to be so I believe that the feeder arrangements, in the centre of the Tower base below, are different from those used on the earlier Reserve site:

Nothing remains of the Transmitter Hut - the wooden structure was demolished and in 1944 it was subsequently replaced by a Nissen Hut housing LORAN Equipment. However, it was protected by a brick  blast wall,  which still remains:
Finding the site of the Receiver Hut is even more difficult, unless you know where to look. Just north of  the base of the Reserve Receiver Tower, a few bricks can be found embedded in the soil giving an indication of where the operators and receiver technicians were expected to work:

The National Grid had not reached as far as Unst by the start of the Second World War so military units needed to generate their own power. To be independent of the main site, the Reserve site required  to produce its own electricity and, therefore, a separate Power House was constructed.

The next picture shows the Guard Post, with the Power House to the left. The headland, which can be seen in the distance, is Lamba Ness, the location of the main RAF Skaw station.
The only other buildings on the Reserve itself visible today were for the 2 x two-seater chemical  WCs at the eastern end of the headland. They were constructed so that windows and doors faced inland to prevent lights shining out to sea and possibly attracting enemy shipping or submarines. I'm sure that the closeness of the sea and the direction of prevailing winds would have been considered when choosing locations for these buildings.

Some distance to the south-west there is a further reminder of the period. A separate Mess Hall and incinerator  were erected but would have seen little use. A  small brick and concrete structure exists  just to the west of the Mess Hall. It may have been for fuel supplies but it is possible that this was put up by later inhabitants of the Haa as storage for the Essy Cart (Garbage Truck). These structures were near the Haa but on the south side of the Burn of Skaw. Personnel would only have used the Mess Hall if the Remote Reserve were to be activated.
The Incinerator lies near the mouth of the Burn of Skaw:

Just to the west of the Mess Hall, in the foreground of the next picture, lies the next object. Its purpose is unknown but, like the main RAF Skaw Station, the Remote Reserve and the WWII  Admiralty Experimental Station on Saxa Vord, it was made using bricks from Edinburgh!

In the areas of the Transmitter, Receiver and the Power House a number of ground-level ducts can be seen. They are of two types: The first type, to provide access to GPO cables and wiring, can be seen in the next picture (which has a distant view of the most northerly point in the UK, Out Stack, in the top left:
The second type of duct was to provide cable access for the RAF technicians. The example in the photo below came from near the base of the reserve Receiver Tower and shows, once again, that some people cannot be trusted near wet concrete - it would be interesting to discover whose initials were inscribed more than 70 years ago! It is quite possible that this duct was made later for the LORAN Transmitter Tower.

There is very little in the operational rerecords of HQ 60 Group, 70 & 71 Wings and RAF Skaw about the Skaw Remote Reserve - not really surprising since  it appears never to have  been used operationally. The Chain Home construction programme was immense and sites received priority in line with the perceived threat and, due to difficult locations, island sites tended to suffer from difficulties in the supply chain.  A few of the details I have been able to glean are listed below:
June '41                RAF Skaw Remote Reserve site chosen
April '43               "Buried "Reserve at Skaw 95% complete -  either "Buried" or "Skaw"  is a  Staff  Officer error I think! 
April ' 43              Good progress has been made with the aerial installation at the Skaw RR
January 44          Remote Reserve Transmitter & Receiver disconnected - ready for removal (HQ 70  Wg)
February '44       Dismantling at Skaw Remote Reserve complete on the 25th
Apr '44                  RR Transmitter Tower dismantled
May '44                RR - second Tower dismantling complete
Jul '44                    7 Jul Work started on AMES713  (LORAN Site) and erection of  a 120' Tower  (Transmitter) - completed in early Sep 44
As there were no RAF personnel posted into the Reserve and, because any army guards assigned to protect the area would not be allowed access to the buildings & equipment, I have found no detailed anecdotes relevant to the site.

Don Wright was posted in to RAF Skaw in March 1942, to work in the Power House. He had previously been an Aero Engine Fitter on an airfield but had experience of working with diesel engines. His wartime story would be worthy of recounting at length elsewhere. He was believed to be the first WWII RAF "incomer" to marry a local Unst girl.  He remained at Skaw to the end of the war, arriving as an airman;  a number of promotions followed until he became the Flight Sergeant in charge of the Power House. He remembers that he and other members of the Power house crew had to go to the Remote Reserve occasionally to start up, run and maintain the diesel generators, just to ensure they were available in case of need.
I have been unable to find out details of the technical equipment installed at the Reserve. However, as it would require to be manned and operational quickly, it would seem sensible that, as much as possible,  it should be similar to the main site. This would enable the operators and technicians to have the place "up & running" expeditiously. There were a number of companies which produced power plant for the Chain Home stations but I know for certain that the generators used on the main site were Blackstone (primary power) and Lister (stand-by). As the LIster Company took over Blackstone in 1937 and were renowned for slightly smaller units, I think it highly probable that the Power House would have had equipment like this installed (Metrovick = Metropolitan Vickers):

If the radar Transmitter and Receivers were the same as those on the main site, they would have looked like those in the pictures below, also reproduced from the SD 0458:
One aspect of the Reserve was a puzzle at first. On the west side of the Power House I noticed parallel lines of concrete and metal remnants:

On closer Inspection similar remnants could be seen all around the building, though the layout didn't seem to be completely symmetrical. Later, more cement and metal was found around the locations of the Transmitter and Receiver Huts . Looking at recent Flash Earth images patterns can be distinguished. With the help of Mike Dean and Bob Jenner it became obvious that I was seeing the perimeter of the camouflage netting.

The 3 views above are seen in perspective below:

The outline of the camouflage for the Remote Reserve Transmitter site seen in the Flash Earth images above can be compared with an early plan, drawn for the Air Ministry in Aug 41.

It's interesting to see that the road/track which had to be constructed can be seen on the right of the plan above. Seventy years later it can be detected visually on the ground, but the further  north of the of the Transmitter Hut you go, the more difficult it is to trace.
So, that's the story of the RAF Skaw Remote Reserve (AMES 56R). It was started in Jun 42 and largely demolished by May 1944,  apparently without any actual operational use. Any research on the site is complicated by the fact that; less than 3 months later, work began on another (even more classified),  unit - AMEs 713. The story of the LORAN Navigational site has been told here:

Previous articles on RAF Skaw

Part 1 of RAF Skaw -
Inception to Jan '41 is here:

Part 2 of RAF Skaw -
Advance CH - From Jan 41 to May 42s is here:

 Part 3 of RAF Skaw -
CH Ops is here:

Part 5 of RAF Skaw - Some of the Other Buildings at RAF Skaw

Part 6 of RAf Skaw - Defence & Protection

Scheduled Monument Status: 
AVIA 7 - 312 Unst, The National Archive
Air 26 - 094 HQ 70 Wg ORB Appendices, The National Archive
AIR 26 - 095 HQ 70 Wg ORB, The National Archive
Air 26 - 100 HQ 71 Wg ORB, The National Archive
SD 0458 - Photographic Record of Radar Stations (Ground), Air Ministry, Aug 43
Building Radar by Colin Dobinson, English Heritage, Methuen, 2010
Mike Dean MBE
Bob Jenner
Leslie Smith
Lexie McMeechan
Rita Carle







Friday, 31 August 2018

A History of RAF Skaw-(AMES 56 ) Part 6 - Defence & Protection

Defence & Protection. Apart from the RAF personnel posted in to run the Chain Home Station, there were a number of groups assigned to protect the site. They included  the Home Guard, Army Infantry, the Royal Artillery who manned the 40mm Bofors Guns and, from 1942, an element of the RAF Regiment.  In addition to these "defenders" all RAF servicemen posted to Skaw were required to participate in ground defence training.

Local Defence Force  (LDV - later known as the Home Guard). Members of the Local Defence Force were usually too old,  too young for the regular forces, or worked in reserved occupations. It's easy to regard them as a bit of a joke following the successful TV series, Dad's Army, but that would be unfair. Many of the older ones had experience of warfare in the First Word War just over 20 years earlier and they would be defending "home" territory. With their UK numbers reaching one & half million, it was a force to be reckoned with. In Shetland they were formed into the 1st Zetland Battalion,  Home Guard, which had more than 1,000 members during the war. One of their tasks on Unst was to man lookout posts and to report any landing of paratroops .
Coastguard. Three Coastguard posts were also manned on Unst throughout the war, at Muness, Hermaness and on the Keen of Hamar. They worked watches, often in appalling weather and it's interesting to note they were armed. Six men were assigned to each post and the main armament was rifles, though a Thompson Sub Machine Gun was assigned to each of the posts at Hermaness and Muness

The Regular and/or the Territorial Army. Over the course of the war a number of companies from different Regiments were tasked with the defence of Skaw and the Admiralty radar on Saxa Vord. I know that elements of the Gordon Highlanders , Cameron Highlanders, Black Watch and the Highland Light Infantry were involved at  different times.
The Royal Artillery presence at Skaw varied throughout the operational life of the Station. In 1941, four Bofors Gun sites were surveyed but whether all were ever used at the same time is another matter. The first 2 guns appear to have arrived in Jan 42 and I believe that they were deployed near the main Power House and just NW of the Transmitter Block. Another gun probably arrived in Mar 42 and was positioned near the Receiver Block. The Royal Artillery had a reputation for being "self-contained",  organising their own food, laundry etc.

 After then the situation is confused - a fourth gun may, or may not have arrived. Four Lewis Guns supplemented the 3 or 4 Bofors Guns on site.  Lewis Guns, of much earlier US design, were mass produced by the Birmingham Small Arms Factory  Britain (also famous for BSA Motor Bikes). They were much smaller calibre (.303 inch) than the 40mm Bofors and much shorter range. In the middle of 1943 the plans stated that Skaw should have One Troop  Light Anti-Aircraft Regt Royal Artillery, with 50 men, 4 Bofors Guns (which could be used in anti-aircraft or ground defence roles), 4 Lewis Guns and 45 Rifles. It is quite likely that the Royal Artillery were withdrawn in 1944 as the air threat to the radar reduced and the need for artillery for the forthcoming invasion of France Increased. From June 1944 a large increase in artillery around the south coast of England took place to help defend the Home Counties against the threat from the V1 flying bombs. A short film clip of a Bofors 40mm gun in 1940, from British Path√©, is here:     

The photo below, from the Imperial War Museum, shows a 40mm Bofors Gun and, below it, a photo of a Lewis Gun, also from the Imperial War Museum:

Army Billets and Buildings. There seems to have been at least 6 billets  and a number of other buildings assigned for Army use. Three Army Billets lay just north of the road, which runs through the camp and were on the main Domestic Site. These would probably have been allocated to the Guard Force. Certainly for a significant part of the War Shetland was considered to be at threat of invasion and radar sites were also thought to be vulnerable to sneak "commando style " raids.
The other three billets (with associated ablutions) are split between three of the sites surveyed for the Royal Artillery for their Bofors  Guns  -  I presume that these were occupied by the gunners. Each of these 3 gun positions appears to have been a "self-contained unit".  However, Ron Simkins , an RAF radar mechanic at Skaw later on in the war,  remembers the most easterly of these billets being occupied by the Highland Light Infantry  - perhaps the Royal Artillery had left and the accommodation had been reassigned - there were many significant deployments around D Day.
The constructions by each of the gun sites were all similar and I have marked the positions  of the billets as A1, A2 & A3 on the following image:

Because they are so alike I will describe the area around A2 as that site seems reasonably well preserved. This is a short distance to the south-west of the Main Power House,  as can be seen on the Flash Earth image below.

Recent photos, showing what remains of these structures, follow:

The final element of the artillery site - the ablutions, were described in the Dept of Works plans as "latrines and drying room". Note how close to the cliff edge it was built:

The actual Bofors Gun hard standing for the site marked A3 on the Flash Earth image a little earlier, was just north-east of the Receiver Block but the actual accommodation site can be seen in this next picture, taken soon after the war and kindly sent to me by the late Norrie Moir:
The RAF Regiment. In Jan 42, King George VI signed a Royal Warrant which brought the RAF Regiment into being. The primary aim of the new force was the defence of RAF Installations against ground and air threats . It obviously took some time to train sufficient personnel and the Skaw records I have seen are short of details but, I know that some members of the Regiment were on the Station in 1943 & 44. I don't as yet know how many of them there were but my late father-in-law, 1554227 LAC Hughie McMeechan, was among their number at Skaw:

2740 Squadron, RAF Regiment was used in defence of Sumburgh and 2751 Squadron was at Sullom Voe.  I'm not sure which Regiment provided the personnel on Unst, but it was possibly 2737 Sqn. This Sqn was deployed to Norway later (so was my  father-in-law). Although the RAFRegiment used a variety of anti-aircraft weapons during WWII, including 40mm Bofors Guns and 20mm Oerlikon Cannon, I think it more likely that they used .303 Lewis, Vickers, Bren or Browning Machine Guns at Skaw, all types being recorded on the Station. In Aug 42, the operational records note that work started "on the 4 gun pits for the motley stalk mountings". In fact, the firm of Motley made a number of different mountings for machine guns, including the Bren gun & the Vickers .303. In this case I believe the text refers to the Motley Stork Mounting, which itself comes in a number of varieties. I have identified three suitable "gun pits" within the Station boundaries and marked them with orange crosses on the Flash Earth Image below, I suspect that they were manned by Regiment Gunners or the Royal Artillery.  There may well have been a fourth position but bricks are a rarity on Unst and someone may well have found a different use for them in the 70+ intervening years!

The next 2 pictures show the exterior and interior of the site gun emplacement closest to the Receiver Block, the other  2 sites are similar:

There is another type of "gun pit"  on the station, also probably for .303 use. These are flush with the ground and offered a certain degree of protection should the site come under attack:
Building used by Guards/Sentries. Some buildings were constructed for the use of sentries and/or the guard force. The main CH buildings would have had controlled entry in an attempt to prevent intruders or inquisitive civilian workmen gaining access. However, there were 5 stand-alone buildings that I know of, intended for use by guards. For simplicity ! will describe them starting from the western end of the Station.
Just to the south of the main entrance to the camp was a wooden Guard Hut. Nothing remains of the hut but its approximate position is marked below:

To the SE of the Power House lies another " Guard Hut", but this time it was a more like a "Guard Post," though small and substantial. It is largely as it was over 70 years ago:

The next "guard hut" is close to the turn-off to the Transmitter Block. I believe that this  building may also have served as an armoury:
Alongside the structure are the foundations of what possibly was a set of ablutions:

The interior of the building shows that it has been used as a shelter by sheep for many years. The rear part of the building, without windows, was possibly used as an Armoury:

The last two "Guard Huts" look alike but are slightly different sizes. Just to the east of the Standby Power House lies the ruin of the next one. In plan it measure about 16'3" x 18'3" and it had a high pitched roof:

At some stage during the war a German Bomb landed close by:
The last of the Guard Huts is about 100 yards NNE of the CH Receiver Block:

It was slightly larger than the one by the Standby Power House, measuring 20'4" x 18'5". It also has a high pitched roof and a raised concrete floor:

 WWII ruin NNW of the Transmitter Block. There are the remains of a number of structures in the area to the north of the Transmitter Block. The largest one, circled in yellow on the Flash Earth Image below, was built during the lifetime of RAF Skaw (same makes of bricks employed - ETNA & EDINBURGH)

 A couple of photos of this follow:

This site does not appear on an Air Ministry Works Department plan, dated 1945, nor is it labelled on a map produced by Ron Simkin after the war. After a long time puzzling I remembered two rectangular buildings of similar proportions at RAF Noss Hill, Shetlands other Chain Home station. A Noss Hill plan names them as "Q Buildings", ie decoy buildings and, therefore, I presume this one at RAF Skaw  to have been built to fulfil the same function.
Camouflage and Barriers. As mentioned elsewhere, extensive use was made of camouflage netting, particularly around the Transmitter Block, Receiver Block and Stand/by Power House. An example from the SD0458 can be seen below (from a more wooded part of the UK):
A photo from just after the war, showing the location of the Stand By Power House, reveals the where the camouflage surrounding the  block used to be :

Camouflage  was not just limited to buildings. Prominent, irregular patterns were often painted on to the ground - anything which might help confuse attacking aircrew.
Barriers were also constructed at possible enemy landing points; for example, a substantial barrier was established across the beach at the Sands of Inner Skaw with the possible  laying of mines on the seaward side. Barriers were also put up across the peninsula of Lambaness from the north to south, allowing defence in depth - they permitted defences to retreat into prepared positions. The picture below is part of 2 photos, given to my late mother-in-law by Leslie Smith. The dark zig-zag line from the bottom left to the top right is one such barrier and what looks like a dotted line across the bottom probably consists of anti tank obstacles. The 2 dark circular areas are bomb craters to the SW of the Transmitter Block, caused when a JU88 attacked Skaw in Mar 41
Decontamination. Many forget that during WWII  servicemen and civilians alike were issued with gas masks and haversacks in which to carry them - they were expected to have them close to hand at all times. Some of the lessons of the 1914 - 18 "Great War" had been studied, including the effects of chlorine & mustard gas,  nearly all military units of any size in WWII had  decontamination chambers. RAF Skaw was no exception. A sleeping shelter which stands near where the camp gates were at the western end of the Station was converted into a Decontamination Chamber. It seems that it has since been used by local sheep for many years:

Air Raid Shelters (ARS). A variety or shelters were erected. Personnel who worked in protected environments like the Transmitter and Receiver Blocks were reasonably safe; whereas, those in wooden or nissen huts at the time of an attack were particularly vulnerable. Three types of ARS are shown below;  the first picture is of the type provided for the civilian Palmer and Cruickshank families - the material for the roof has obviously been "salvaged":
  The next shelter illustrated is from near the area of the smaller domestic site, about 200 yards SE of the Main Power House - some of the roof remains in the vicinity:
The final ARS photo shows the largest of the three and it is relatively intact. There is another, similar one, with both of them being on the westerly Domestic Site. Like many buildings on the Station it has long been used by sheep - good waterproof boots are recommended!
At the beginning, when the construction of RAF Skaw began, the threat of attack by German forces was considered to be great. Barriers, anti-tank traps and the use of mines helped deter sea-borne landings and continual surveillance from the Coastguard, Naval vessels and Coastal Command aircraft would, hopefully, provide early warning. In 1940 the use of  Fallschirmj√§ger (Paratroops) was extremely effective in the German invasions of France, the Netherlands and Norway. The use of glider-borne infantry was also successfully demonstrated in the German capture of the Belgian fort of Eben Emael in May 1940. It's no wonder that troops like the Home Guard throughout the UK were trained to meet such threats. Many fields in Unst, which were relatively flat, had rows of stakes erected to hinder landings and special Home Guard Observation Posts were manned. Two of the Unst fields where stakes were placed can be seen in the 2 images below - there must have been many more! er
Part 5 of RAF Skaw - Some of the Other Buildings at RAF Skaw
Papers of Major Denis Rollo - Held by The Shetland Museum and Archive
Mr Leslie Smith
Rita Carle
The Late Norrie Moir
The late Lexie McMeechan
The Late Ron Simkin
Unst Heritage Centre
Mike Dean
Bob Jenner
SD 0458  - Photographic Record of Radars stations  (Ground) - Air Ministry Aug 43Imperial War Museum