Monday 30 April 2018

Admiralty Experimental Station 4 – Unst - 1940 to 46, (amended April 2018) - Part 1

Since an article about the Admiralty Experimental Station No 4 (AES4) was first issued in July 2012, I have been fortunate to gain access to much more material. In particular, new information and pictures have come from the Unst Heritage Centre, the collection of the late Lt Richard Feachem RNVR and from Sqn Ldr Mike Dean MBE. Due to software limitations of the Blogger software it has become necessary to split the article into 2 parts - Part 2 is here:

Very shortly after the start of WWII, Vice Admiral Sir James Somerville, who was in charge of the Directorate of Anti-Submarine weapons and Devices, witnessed a trial off the Suffolk Coast where a radar was used to attempt to track a surfaced submarine. The trial was successful enough to persuade him that radar could be a significant help in countering the U Boat threat. There were concerns about defence of the Home Fleet – 2 U Boats (U-18 &  U-116 had attempted to penetrate Scapa Flow in WW1 and there were worries about U Boats and surface vessels entering the Atlantic in an attempt to cause  disruption to Allied shipping. It should be remembered that, unlike modern submarines, most long distance travel by U Boats was done on the surface – the ability to remain submerged for long periods was limited – the crew members simply ran out of fresh air to breathe. Even with a snorkel, submerged time was limited and, though not large, snorkels could sometimes be sighted or detected by radar.

Somerville decided that a chain of 6 Coastal Defence U Boat Radar Sites should be built in the North of Scotland to help protect Scapa Flow and to provide a watch for U Boats/enemy shipping  transiting between Shetland and Orkney or passing just north of Unst. The most suitable equipment available at the time was that planned for the RAF Chain Home Low (CHL) sites. The Naval sites, which were originally developed separately from the CHL sites, were known as Admiralty Experimental Stations (AES) and they were each allocated a number. The site on Saxa Vord was AES 4, usually known as Saxavord (all one word) by the Navy. Radar production for all 3 services required a large construction programme, gun-laying radars, ship borne radars, radars against high and low flying aircraft were all needed. Priorities changed as the threat was continually re-evaluated and so, where there were similar roles, radar originally intended for one service, was sometimes diverted to another project belonging to a different service. Some equipment was interchangeable but not necessarily identical. The Naval CDU sites, whilst similar to the RAF CHL sites, sometimes had different equipment

The map below shows where these Naval units were built. The ones at Dunnet Head and South Ronaldsay were primarily established to protect Scapa Flow. The 2 sites on Fair Isle and the one at Sumburgh were to provide surveillance of the waters between Orkney and Shetland.  AES 4 at Saxa was to watch for traffic to the north.


The sites were constructed in 2 phases and the programme was carried out swiftly. AES 1, 2 & 3 (Sumburgh and the two sites on Fair Isle) were built in the first phase. The earliest to become operational was at Sumburgh which was opened in Dec 1939 – just over 3 months from conception to completion.  Later in the war the Sumburgh site was moved nearly a mile northwards to Compass Head and was transferred to the RAF as RAF Grutness. The second phase included AES 4, 5 & 6, with the last of these 6 sites, at Dunnet Head (AES 6),  becoming operational in Dec 1940.

The daring raid of the U47, Captained by Günther Prien, which penetrated Scapa Flow in Oct 39 and sank the Battleship HMS Royal Oak, is told in other places. Would the Coastal Defence Radars have made a difference had they been operational earlier - who knows?

It is tempting to try to recount the history of all AES CDU sites but I currently don’t have the data or time to tackle the task.  In passing its worth mentioning that there was a later 7th AES CDU built, but that was in NW Iceland at a place called Sæból, where its primary role was to monitor traffic in the Denmark Strait. From here on, this section will be directed towards AES 4 on Unst.

In early 1940 Vice Admiral Somerville and a small party studied a number of locations on Unst (incl Clibberswick – 160m/525’ ASL, an unnamed site about 1 mile west of Outer Skaw and at Libbers Hill - 170m/558’), before selecting Saxa Vord as the most suitable site for the radar. At 285m/935’ the summit is the highest point on Unst and it was deemed to provide the best coverage for the equipment to be installed. The following photo, sent to me by Sqn Ldr Mike Dean MBE, is of great historic interest. It shows the original reconnaissance party en route to survey the Saxa Vord site in Jan 1940. I believe the group shown includes Vice Admiral James Somerville, Lt Richard Feachem RNVR and Lt Evans RNVR. The Admiral, and possibly the same group of men, carried out a similar mission on Fair Isle also during January. Lt Feachem enjoyed the distinction of being selected to serve on all 7 Admiralty Experimental Stations at different times during the war:

The very small structure that can just be seen on the summit of the hill is nothing to do with later radars, I believe it was a cairn that can be seen in this photo, dated 1938, which is held in the Shetland Museum Photo Archive:

A substantial track, constructed in WWI and known locally as Whites Road after the officer responsible for having it laid, led up to near the chosen radar site. It had been made to enable a gun to be deployed to cover Burrafirth in case enemy shipping attempted to use the Firth for shelter.  Between the two wars the local population used the route to access the plentiful peat banks on the hill. This track had to be extended and improved before construction of AES 4 could commence.
As with the later RAF Station, the Admiralty “top site” was built in 2 parts. The lower section was where the generator and accommodation huts were located and the upper area, where the radar equipment was to be installed. There was no road between the 2 sites as there is now and so a 2ft gauge rail track, approx 120 yds/110m long, was laid between the 2 sites. Similar rail tracks were needed at some of the other AES  units and we are fortunate to have the following picture, once again from the collection of Lt Richard Feachem, of the track at AES7 in Iceland:
All heavy items had to be winched to the upper level. Initially all the material for two  brick buildings, each 16’ x 16’ and 10' high for use as Transmitter and Receiver Blocks, plus all the CHL radar equipment had to be moved. Each of the Blocks had an aerial gantry built over it. The gantries were similar to the one in the photo below, though the one shown was on Fair Isle. The picture gives some idea of the construction techniques which would have been available at the top of Saxa:
Inside each of the blocks an operator had to rotate the aerial using apparatus similar to that which drives a bicycle except, in this case, it was hand turned. The equipment was designed at Cambridge under the auspices of Dr John Cockcroft who, much later on, was awarded a Nobel Prize for his work on Nuclear Physics. The actual gear in the photograph was at the CHL site at Worth Matravers, near Swanage, and the picture was taken in Nov 40, just a few weeks after AES4 opened.
At the top of the chain was a gearing system which looked like this:

 The rotation had to be co-ordinated to ensure that the Receiver Aerial was aligned with the Transmitter Aerial. The radar beamwidth, at around 30 degrees was wide, so exact alignment, although much preferable, was not always essential. The Receiver Block also acted as the Ops Block and for some time the radar display would have been a simple A Scope. To begin with it would have been from here that the Units single telephone line ran to the manually operated civilian exchange in the Haroldswick Post Office. From Haroldswick the calls had to be routed via normal GPO lines to the Naval HQ at Fort Charlotte in Lerwick. Later the telephones were linked to the system which ran from RAF Skaw CH Station.
Whether afloat or on land, naval personnel were assigned to a “ship” for administrative and accounting reasons. During WWII the Royal Navy personnel on Shetland were considered to be on board HMS Fox (shore based establishment – HQ etc). The crews of naval Coastal Defence Forces – Motor Torpedo Boats etc were considered to be aboard a Tender to HMS Fox called HMS Fox II. The establishment of the CDU would also have been considered to be a Tender to HMS Fox and personnel would have had cap bands saying either “HMS Fox” or possibly just plain “HMS”.
AES 4 became operational on 24 Sep 1940 and was manned by Royal Navy personnel, with support from RAF and, later, RCAF mechanics. One of the Canadians, Puss Valeriote, made a nostalgic return visit to Unst in June 2000. The Unit remained on the air for a short while after the war in Europe was over in May 1945. Its work had not been limited to searching for submarines and surface vessels – the radar had quite a useful capability for detecting airborne targets. By the end of 1940/early 1941 the radar was detecting shipping out to the radar horizon, 40 miles or more depending on the size of the ship, though for smaller vessels such as trawlers, ranges of 25 to 30 miles were normal. Aircraft below 10,000 were being seen at around 100 miles but performance of the early CHL radar was not very good against higher flying targets. By the end of 1941, following updates to the equipment, ranges against airborne targets had increased considerably with ranges of 140 miles reported.
In the early years of radar, developments and improvements were taking place rapidly and units, like AES 4, were frequently upgraded. The first major change at Saxa was the changeover from 2 aerials to a single aerial. It would have been sited at the Receiver Block. This change was made possible by the introduction of a new Transmit/Receive switch and new feeder arrangements for the aerial. Later, much better Transmitter valves were installed. Manual rotation of the aerials was replaced when powered turntables were introduced
Evidence that the Receiver Block was extended to house the transmitter equipment can be seen in this much later picture, where the foundations of the extension are still visible to the right of the block.
Whilst I don’t have a photo of the interior of an AES Receiver Block the photo below was taken inside a similar sized building at the RAF Coastal Defence/CHL radar unit at Dover. The person on the left in the picture is Flt Sgt Wray and the picture gives an indication of the limited working space available.
In 1942 an even larger upgrade commenced. Work on new structure, known as a Combined Transmitter/Receiver Block or sometimes as a 1941 CHL Building, began. This was located half-way between the Receiver Block and the old Transmitter Block. It was much bigger; measuring 50 x 18 ft. RAF Chain Home Low sites would normally have a radar, like the one in the photo below, associated with the new type of Building (the small aerial on the building itself is an IFF antenna). Although I have not been able to establish its exact location, one of these aerials would have been sited fairly close to the new block at AES4.

However, the Navy decided that they would like to add one of their own radars, a Navy Type 273. This radar was specifically designed for use against surface and low level targets and belongs in the group of radars the RAF knew as CHEL (Chain Home Extra Low). This decision was unsurprising as the detection of U Boats and enemy shipping was the main purpose of the Unit. This equipment was more usually carried on board ships. I don’t have a photo of one mounted on a 1941 CHL Building but photos of ship borne equipment follow:


 The “tube”, made of Perspex, was known as a “Lantern”. Inside was an S band radar very unlike the RAF CHL equipment. The installation would have been like that shown in the next 2 pictures:

Because this was not a “standard fit” for the 1941 CHL Building, the structure at Saxa had to be modified and a small extension was added to the north side. The following pictures, taken at much later dates, show the extension and the aerial mount.

To give you some idea of the difficulties faced I have included a photo of a similar radar to the Navy Type 273, one of its forerunners the Type 271, on the back of a lorry. The problem of winching something that size and weight up a very steep slope on a 2ft gauge track is obvious.

The new equipment would require more power than the generator on site could produce and so it was decided to lay a power cable from the Power House at the RAF Skaw Chain Home site, 2 miles away, up to the top of Saxa Vord. The track of the cable can still be seen 60 years later – it’s just to the left of the white lines in the next photo, which was taken in Mar 2012.

The “dog-leg” in the track shows where it crossed the Burn of Skaw. The cable was removed long ago as part of an official contract and the copper recycled.

In the following photo the ruins of the RAF Skaw Power House can be seen with Saxa in the distance:

© Copyright Mike Pennington and licensed for reuse under this Creative Commons Licence
 The work on the 1941 CHL Building, RN Type 273 and power cables took the best part of a year and the radar was actually ready a couple of months before the new power supply could be connected. The new system became operational early in 1943. I don't have an exact date that the NT273 became operational but the RAF Skaw Power House log has an entry on 11 Feb 43 which states, " Saxa alive at 13.45hrs (¼ load)". Regrettably, I have no photos from the inside of a Naval CDU/CHL 1941 Building. The next 2 pictures are of the inside of a similar building on an RAF CHL site (no Type 273 Radar on the roof but some of the RAF sites had an early type of IFF aerial in a similar place, as seen in a previous photo). The main division of the building was into a Transmitter Room and a combined Receiver/Ops Room.

 As seen on the right in the previous picture - at the really “sharp end”, the radar consoles would have looked like this - the range tube on the left and the PPI (Plan Position Indicator) on the right:


Whilst this work on the  CHL 1941 building was being carried out another structure was taking shape to the north-east of the Transmitter Block. A separate Mark III IFF (Identification Friend or Foe) installation was added to the site. The small building, known as a kiosk or cubicle was complete by Sep 1942, at which time the foundations for a 28ft mast were being laid alongside it. I’ve not been able to establish exactly when the actual equipment arrived on site, IFF Mk III was much in demand at this stage of the war and the allocation of IFF sets was prioritized between the various service requirements. The completed installation would have been like the one in the picture below – if you use your imagination and remove the trees!

Although the mast was removed at the end of the war, the kiosk remained until 1983.

To summarise the AES 4 structures, I have added a labelled extract from a May 1946 over flight photo.

A different extract from the same over flight photo shows both the radar site and the site where the generator and rest huts were located. The road down to Haroldswick is just where it is today. At the extreme right of the picture, beside the road, some construction work can be seen:

I believe that water was collected from a spring in this area and pumped to the site - there are records of up to 800 gallons of fresh water a day being provided to AES4. In later years a pump house was built in the same area to help provide RAF Saxa Vord Ops & Tech sites with fresh water. The picture below shows the later RAF Pump House and I  believe the arrow indicates the bed for a generator used in the supply of water to AES4 :
Defence of the Operations Site. The provision of anti aircraft weapons for the radar site was examined by Admiralty Staff during much of 1940. In the end it was decided, because nothing more modern or effective was available, to issue the Unit with 2 Hotchkiss Mark 1 Star machine guns. These were French designed and of WW1 vintage. The particular model available was of British manufacture and had a .303 calibre. One thousand rounds per gun, plus mountings and loading equipment were supplied.

There were also  many discussions early on in the war about providing a Royal Marine guard force to protect the operations site. However, it was decided that it was the responsibility of the Army. Platoons from a number of regiments carried out this task, including from the Seaforths, Royal Scots  and Gordon Highlanders (many of the personnel were from the Local Defence Force/Home Guard).  At one stage the Gordons were commanded by a certain Captain Conochie, a name which was to become familiar to many who used Commercial Street in Lerwick in later years. A barbed wire barrier was erected around the site and machine gun emplacements constructed, (the army guard force would have had their own weapons).  Later on a second barbed wire barrier was added. Very little sign of the defensive structures can be seen nowadays but there is anecdotal evidence which suggests that some concrete remains behind the more recent RAF Saxa Vord Fire Section were part of an AES4 defensive position:
The operations were run by the Royal Navy with, as mentioned earlier, technical back up from the RAF and RCAF.  There were occasional sightings of enemy aircraft and, in 1941, a Heinkel III dropped a single bomb near the Transmitter Block – luckily no damage was caused. RAF Skaw saw slightly more enemy action than Saxa but the uncertainty would have been the same whichever site you were on.
There were few people on strength when operations started and the site had to be run on a 3 watch system, one watch at work, the second at the Rest Hut below the Tech site, in case of inclement weather etc, and the third off-duty in Haroldswick. The Navy had been lucky enough to take over a decent sized building at Haroldswick called Hamarsgarth, this is where the off-duty personnel were based. As time went on the number of personnel increased and the watch-keeping duties eased a little. The location of Hamarsgarth is illustrated in the next (modern) picture, which also shows part of the route up the hill to the radar site.
By late 1942 Hamarsgarth could no longer cope and two huts, 2 nissen huts and a garage had to be built to accommodate the overflow.  The next photo, taken by Lt Richard Feachem RNVR, one of the Commanding Officers, shows Hamarsgarth during the war, with a wooden hut on either side:

Another photo from Lt Feachem, is of the rear of Hamarsgarth - with a Nissen Hut just visible at the left:

The Unit never had a large complement, being commanded by a Lieutenant with a Chief Petty Officer as his deputy. As the only Navy Unit on Unst, the staff were involved in the reception and provision of assistance to significant numbers of refugees escaping from occupied Norway in small boats – this task could be quite time consuming and the fact that the refugees included women and children made it more complicated. The picture below, once again from the collection of Lt Richard Feachem RNVR, shows one of the boats used by Norwegian refugees which only just managed to reach Unst. Unluckier refugees sometimes drifted north of the island and were fortunate if they eventually reached the Faeroes or Iceland. This vessel sank alongside the pier and lay on the rocks. The two on the boat are an RN cook called Marks and, beside him, Royal Marine Fred Walsh - a Driver - who was  the only man among the navy CDU crews to be honoured  for his work during WWII.

To help in the feeding, clothing and processing of these Norwegian refugees the Commanding Officer of AES4 was nominated as an Honorary Norwegian Vice-Consul. The extract from a 1941 Alexander Sandison & Sons ledger, shown below and held in the Skibhoul Archive, shows some of the transactions carried out on behalf of the refugees - I don't think the current  Norwegian Government would approve the expenditure for 20 packets of cigarettes! :

Among the naval personnel was Chief Petty Officer Stoker Alfred King. He was a large man and older than the rest. He had served previously and had been on the naval reserve before the war - in civilian life he had been a butcher. He became well known locally and amongst the servicemen on Unst, in fact many feared him due to his 20 stone frame and his reputation for a ferocious nature. He is most remembered for organising the rearing of pigs (and their slaughter), at Hamarsgarth. The photo below comes from the collection of the late Geoffrey Sleigh and shows one of these animals at Hamarsgarth (perhaps close to its last days!).

Some of the pork produced was eaten by the men but rumours persist that some was used for local barter. Possibly in the hope of currying favour, a special ham was sent to the Admiral Commanding Orkney and Shetland. The men of AES4 must have become fairly self-sufficient in providing calories from themselves and the output increased as the war went on. Hens were kept for their eggs and meat, there are even records of the rearing of ducklings and gosling - some of the crew, with Geoffrey Sleigh at the back, on the far right:


Some of those who served at AES4:
Lt J Addison Lewis      1st CO

Lt J Angus Orr             2nd CO arrived Jan 42

Lt KD McInnes            3rd CO arrived 28 Mar 43 (referred to as Lt Ennis by some)

Lt RJ Wilkinson          Relief vice Lt Orr - Aug 42 , returning as the last  CO (44/45)

Lt Richard Feachem   Relief CO vice Lt Lewis - Mar 41 and visited on technical duties Jun 42

Lt Parker                      Relief vice Lt Orr - Dec 42/Jan 42

Lt N Astley                  Relief vice Lt Wilkinson

Lt C Evans                   Technical Visits

Lt Munro?

Sub Lt Corbett             Mid '41

Dickie Blackmore        (an officer)

Chief Petty Officer Alfred King

Petty Officer (Radar)  JW Sheard - arrived May 43

Petty Officer Wilson

Cpl Freddie Batchelor (RAF Radar Mechanic)

Cpl Black                     (RAF Radar Mechanic)

Fred B Grahame         (RCAF - detached from AES1 - Radar Mechanic)

PT "Puss" Valeriote    (RCAF - Radar Mechanic)

Micky Porter               (Radar Mechanic)

Jack Diamond              (Radar Mechanic)

Paul ?                          (Radar Mechanic)

Tubby Lucas               (Telegraphist)

Fred Walsh                 (Royal Marine Driver)

? Saxby                        (Royal Marine relief Driver)

Danny Cook                (Royal Marine)

Bill Davidson              (Leading Seaman)

Ken Platt                     (Leading Seaman)

Jack McEwan              (Leading Seaman)

Jack Warner                (Leading Seaman)

Shorty Hargreaves      (Leading Seaman)

SD Way                       (Leading Seaman)

Doug Spinks                (Leading Seaman)

Tony Broughton         (Leading Seaman)

? Birkett                      (Leading Seaman, Radar)

? Davidson                  (Leading Seaman, Radar)

G Wilson                     (CD Radar)

Arnold Layton            (Able Seaman)

Stan Pearson              (Able Seaman)

Frank Dunn                (Able Seaman)

Reg Ormston              (Able Seaman)

Frank Longstaff (Ginger)        (Able Seaman)

Pablo Ablon                (Able Seaman)

Taffy Lewis                 (Able Seaman)

Cliff Slater                   (Able Seaman)

George Lovegrove      (Able Seaman)

Stoker Heaps              (Able Seaman)

Fred Boulton              (Able Seaman

E Graystone                (Able Seaman

? Marks                       (Cook)

Bill Stewart                 (Cook)

Phil Burgess

Geordie Kay

Rattler Morgan

Sam McClumont

Bob Tenant

George Crompton

Bill Wheeler

Geoff Hurst

Tug Wilson

Eric Mosley

Sid Harrop

? Newberry                 (Leading Telegraphist

W McNamara             (Telegraphist)

RJ Hawkins                (Telegraphist)

Geoffrey Sleigh          (Able Seaman)

The last two people on the above list, Geoffrey Sleigh and RJ Hawkins, recorded some of their memories from their time at AES4 and I have added parts of their stories as Notes 1 & 2 at the end of this article.

Whilst there were advantages with being close to RAF Skaw, inter-service rivalries occasionally surfaced – nothing has changed. Very infrequently, there would be local dances or shows from ENSA (Entertainments National Services Association), to which the navy personnel were usually invited. Although ENSA had some very good and famous artists on its books they were spread thinly – leading to the acronym being changed by many servicemen to "Every Night Something Awful". Despite the fact that most personnel were a long way from home, a few of them developed an affinity for the islands in the same way that RAF personnel at the later RAF Saxa Vord did.

Part 2 of this article is here:

I must acknowledge the assistance I have had in writing this article. A number of people have allowed me to use their research and material. In particular, I would like to thank:
The Unst Heritage Centre

Richard Charles Feachem, for allowing me to use material from his father, the late Richard William Feachem

The late Geoffrey Sleigh

RJ Hawkins

Bob Jenner

Sqn Ldr Mike Dean MBE

David Waters

Irene & Tony Mouat

Karl Temple

Other Sources:

ADM 116 - 4275 Admiralty Experimental Stations - Defence

ADM 116 - 4897 Admiralty Experimental Stations 1940 - 1944

AIR 26 - 092 - 70 Wing - Inverness

SD 4058

However, I accept responsibility for any mistakes and will be happy to make corrections where necessary.



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