The Secret Listeners WW2

The Radio Security Service was a WWII secret organisation, the existence of which was not revealed until 1979 (several years later than Ultra and Bletchley Park). These pages explain how several thousand Morse Code readers, mainly licensed radio amateurs, penetrated the enemy secret services and had as a result a profound influence on various military operations, especially the Normandy landings and beyond. A total of 268,000 coded messages, picked up by these amateurs, were decoded at Bletchley Park. Read about how some 1,500 Voluntary Interceptors eavesdropped on the various enemy secret transmissions by listening to short wave radio signals in complete secrecy yet in their own homes. As time passed, full-time monitoring took place in several purpose-built stations using the best possible equipment and aerials. Without these skilled operators, the control of German spies in this country would not have been possible.

EARLY BEGINNINGS

The seeds of the Radio Security Service were sown by MI5 in 1938 when they became concerned about German wireless agents operating in Britain. But a Col. Adrian Simpson sent a report to the Director of MI5 in August 1938 explaining that the interception of short wave transmissions would be difficult and he proposed a network of voluntary interceptors, which he predicted, would probably cover most of Britain. Up to that time they relied on three direction finding stations built and operated by the GPO. This was the beginning of the RSS and a small group of RSS officers joined the officers of MI5 in a group of unused cells at Wormwood Scrubs Prison in London.

THE ROLE OF VOLUNTARY INTERCEPTORS

The Voluntary Interceptors eventually grew in number to around 1,500 including many members of the Radio Society of Great Britain, experienced amateur radio operators who used their own equipment initially and later radios provided by the RSS to listen for enemy agents transmitting within the UK. At the same time the GPO began setting up several intercept stations for RSS and it was not long before the amateurs and the GPO operators started to notice a series of German transmissions which used Morse conventions used by amateur operators such as the “Q” code, but which also included a series of 5 character groups.

The use of amateur radio operators who used Morse code reception as a hobby might surprise some, but their determination to identify weak signals amongst heavy interference, and to track those signals using radio receivers of the day which were not very stable, was what their hobby had trained them to do to a very high standard.

DECODING THE MESSAGES

MI5 had already begun to operate their first double agent in 1938 and using the codes supplied to them by the Abwehr (the German Secret Service). The groups of characters in the messages were decrypted and found to be communications

between German Agents in Europe and their handlers in Germany. Later messages contained Enigma encoded groups. As RSS grew in numbers, they had to move to a large house called Arkley View near Barnet, North London using the postal address Box 25, Barnet. It was here that the intercepted traffic was sorted and analysed and the volunteers' efforts were coordinated. Encoded messages were sent to Bletchley Park for decoding and onward transmission to the Allied Commanders and the Prime Minister, Winston Churchill.

The value of the decoded message was soon appreciated and RSS focussed on Abwehr traffic and that of their rival the Sicherheitsdienst operated by Himmler and the S.S... Other functions were added during the war years.

MOVE TO MI6 In 1941 RSS was taken over by MI6 and it became one of their Special Communication Units, SCU3. They also ran other SCUs that maintained communication with our agents abroad and dealt with wireless propaganda. In addition, MI6 ran SLUs Special Liaison Units that were responsible for disseminating the intelligence from intercepted messages to our military commanders in the field. All of these organisations were under the control of

Brigadier Richard Gambier Parry, MI6's Head of Communications.

Left: What a German Spy might look like whilst operating.

The Origins of Wireless interception and the Radio Security Service.

The idea of listening in to other people's wireless communications dates back to the beginning of wireless (or radio) communication itself. Thus when necessary the messages were encoded and this made it all the more desirable to find out what was being said. Just when it was first suggested that Radio Amateurs should be used for interception purposes is hard to determine and probably pre-dates this 1938 memo: Adrian Simpson’s report to the Director of MI5 dated 10th August 1938 can be

regarded as the real starting point of the Radio Security Service (RSS). From the outset he appreciated that interception of short wave transmissions would be very difficult unless there was a receiver within 10 miles that could detect the ground wave. He proposed the plan for a network of Voluntary Interceptors, which he predicted, would reach considerable proportions and, if possible, cover the whole country. The Radio Society of Great Britain was approached with a request to sound out trusted radio amateurs to see if listening could be arranged on a voluntary basis. Fortunately although their transmitters had been impounded at the outbreak of war they still had their receivers and they could all read Morse code with a particular in reading faint signals in noisy backgrounds.

Each amateur was checked on MI5 records and visited by the local police to see if there was any reason why they could not be trusted. Before long there was quite an army of amateurs diligently searching for spies, that didn't exist, or the suspected transmitters guiding enemy aircraft to worthwhile targets. The amateurs were given the title Voluntary Interceptors (VIs) and were empowered to enter premises where a suspicious transmission was found. As they were not armed it was a wise precaution to have the company of a police officer. In time a few hundred amateurs were asked to listen on HF for anything they could not recognise as genuine commercial or military transmissions and send them in by post written on a log sheet provided, that showed date, time, frequency and what was heard. A few experienced people in Wormwood Scrubs checked the resulting logs and notified the amateur where they were not wanted or further intercepts were required. The organisation was given the title of the Radio Security Service (RSS) but it became apparent that the reason for its existence was false and there appeared to be no reason for continuing. Already the armed services were setting up their own stations to expand the monitoring of types of military transmissions and there was a long established de-coding department in room 40, as the department was called, in the Admiralty building. The Post Office and the Police had radio operators routinely checking the air waves so the RSS was out of a job. It transpired that all was not lost: the amateurs were not put out of work by any means. They were logging whatever was heard and amongst it all located some strange stations using Ham Chat but with 3 letter call signs and on top of that sending messages in 5 letter groups of code. This was strictly forbidden for amateurs. However MI5, located in Wormwood Scrubs prison (with cells for offices) were in charge of looking at these reports (called logs sheets) where Lt. Hugh Trevor-Roper (later Lord Dacre) in concert with Cpt Gill worked on the messages and actually managed to decipher some to discover that they were in a hand cipher that translated into German. Moreover the translation showed that they were not ordinary signals but apparently coming from the German Secret Service (called the Abwehr) or something equivalent to our MI6 only more widespread to include other unpleasant organizations set up by the Nazis. Bletchley Park, previously uninterested or too busy, immediately took note and required all future messages to be sent to it and strictly no more self-styled de-ciphering was to take place.

It became apparent that there was a lot to be uncovered about these secret transmissions and amateurs were recruited as VIs on an ever-increasing scale to

cover the British Isles. Ultimately about 1,700 were engaged on intercepting although not at one time as many were called up, some for other duties, but many to work full-time, in uniform, for the RSS. As the organisation grew it became necessary to set it on a semi-military footing with full time operators and other staff The one thing Bletchley Park could not decode were the signals that it did not receive Here it must be born in mind that there was no suggestion of picking up signals from abroad that came later, but to locate the (supposed) enemy within the UK. This page from the meeting is an early reference to using amateurs (surprisingly a remuneration was suggested) to listen for local signals: The Radio Security Service expands and becomes recognised. Owing to air raids and the need to expand it became apparent that Wormwood Scrubs was not ideal and M.I.5 moved out to various other sites. The RSS was taken over by M.I.6 or Secret Intelligence Service (SIS) as it was widely known. A sub-section of M.I.6 was taken over by Brigadier Gambier Parry and labelled Section VIII. This was further divided into Special Communication Units (SCU) and the two dealt with here were SCU3 and SCU4 the RSS moved on October 3rd 1940 into new headquarters at Arkley View, within a large site 2 miles north of Barnet. This building was already being used by the Post Office as an intercept station. The ‘View’ housed the analysis, intelligence, direction finding control and various administrative departments.

Huts were erected in the grounds for intercept work, a teleprinting terminal, and later the ever-expanding departments to identify, classify and collate the enormous secret intelligence enemy radio networks. The secret cryptic address became well known to the select as PO Box 25 Barnet, this being the new postal address for V.I.s. Arkley View was on the right of Barnet Road leading to Stirling Corner. Arkley Lane had the View on its left and Oaklands to its right. Here was accommodated the orderly room and the despatch riders’ base for taking intercepted messages to Bletchley Park. Officers’ and sergeants’ messes were in Scotswood opposite the View. Other large houses such as Rowley Lodge, The Lawns and Meadowbank were used as billets, messing, transmitting and training schools. In Ravenscroft Park, High Barnet, a billet, operators’ evaluation and a small intercept training station were established, run by CQMS Soames (later transferred to the Lawns). Arkley Organisation

The large country house, Arkley View, was known to all SCU3 enlistments, as the induction to this branch of M.I.6 invariably took place here. Enrolled initially by Lord Sandhurst, soon to be followed by Captain (later Major) Bellringer, a short black-moustached officer, recruits took the oath and the King’s shilling, which is where the resemblance to the generally understood army finished. The account of one early enlistment can be read here. A ‘normal’ army enlistment was provided with an Army

Book 64 (AB64) parts I and II. Part I contained such personal details as date of birth, service number, rank with promotion dates (if any) and the date when various chemicals were injected to protect the recipient from all the various bugs which arose from service to one’s country. This concern for his welfare was followed by details of his next-of-kin and an invitation to write his will, (acceptable without a witness). However SCU prospective soldiers did not receive AB64 part II because this gave a record of pay which in this case did not come from Army funds but from the Foreign Office. This presented a problem for overseas postings which was solved by issuing part II and paying the army rate at the usual pay parade. The recipient was required to open a bank account at home to accept the balance of his RSS-enhanced pay.

Lt Colonel Morton Evans (amateur licence GW5KJ) was made Deputy Controller of the RSS and served as officer i/c at Arkley from 1941 to 1946

Under Lt Colonel Morton Evans the various departments were mainly located in one-storey buildings each about 100 feet long, at the rear of Arkley View house. These were called huts and were frequently extended, as the need arose, in a similar manner to Bletchley Park. Under the general heading of Discrimination were the departments General Search, Groups, Collation and Allocation. Reports from interceptors came to Arkley where, after processing as explained below, copies of the same messages from different intercepts were compared to enable a good copy to be forwarded to Bletchley Park. Initially the intercepted messages came in from the VIs, working at home in complete secrecy and using whatever time was available. Many had full-time employment but others who were retired or disabled could devote more time to listening on the receivers that they had previously used as Radio Amateurs. At Arkley it was realised that for full coverage of the ever expanding German secret networks some form of 24 hour watch was required and in different parts of the UK in order to maximise the amount of information we could obtain. More details follow later.

General Search

The principal work was the scrutiny of logs and the placing of the intercepted messages in the relevant groups. Box 25 received a thousand or more log sheets

daily from V.I.s and the full-time interceptors. These had to be examined to identify new Abwehr services and to sort the familiar ones into their allotted groups. More than 14 different groups had been identified, each having a number of services from perhaps a dozen to a hundred or so. Hence if General Search labelled a message 2/153 it would mean group 2, usually Berlin, and service 153 which could be a link to, say, Madrid, Oslo or Milan. The identification was by means of time, frequency, type of procedure (or preamble if there was a message) or possibly the call sign. This latter was problematic as often call signs changed daily. One task was to examine logs for intercepts which had not been positively identified and to try to discover where to place them or even if they were wanted by us at all. If the operator sent us a previously identified station we sent the details to the relevant Group Officer, located in the next hut, who would then advise the operator whether it was ‘already covered thanks’ or ‘still wanted’. He would have from two to a dozen staff according to the group size. A large wall map was kept in the ‘Group’ hut with coloured wool stretched between points showing the location and working of the various stations. To prevent a casual visitor from seeing the extent of our discoveries, this map was covered with a curtain which was activated by an electric motor. No doubt the local wool shop did not ask questions. If it had, there would have been a ready misleading answer. Log sheets were stamped as ‘suspect’, ‘watch please’ or ‘unwanted’ if due to be returned to the interceptor. If the signal was not the enemy secret service we used the ‘unwanted’ stamp. Other stamps were: ‘unwanted Hun’, ’more please’ and ‘OK covered thanks’.

Typically the transmissions in which we were interested looked radio-amateur style as the photograph shows

This log shows Ham chat such as sri, pse call, nw, 73 (73 is Ham Chat for Kind Regards) but QSA not QSA0 and QRX but not QRX NEXT were used by amateurs. And certainly not a three letter call sign such as CZE and - horrors - sending five letter blocks of code. Any kind of code was strictly forbidden for amateurs. So there was no doubt about CZE and URK being something unusual.

It was important to find out who was 'working' whom. As the frequencies and call signs were constantly changing the only common factor was time and possibly operating procedure. Types of preamble and times and frequencies had to be memorised by the staff, who used card indexes for reference. This work could be tedious and tiring as hundreds of log sheets were scrutinised for the brief suspect transmission. Expansion to 24 hour 7 day intercepting. It became apparent, quite early on, that VIs could not cover all that was required to understand the Abwehr and to penetrate the German secret intelligence networks. Full-time operators working eight hour shifts were required and purpose-built large huts were equipped with the American first class HRO receivers. Five or six larger stations were spread widely over the UK with up to 32 receiving positions, each with two HROs: two HROs because it could be possible to listen to both

ends of a contact. Sometimes a few other types were to be seen such as the AR88 or the British Eddystone and Marconi models. Barnet, Hanslope and St Erth (shown here) These were working by 1942 and other large stations were at Forfar

and Thurso in Scotland and Gilnahirk in Northern Ireland. The operators were recruited from several sources although mainly from the ranks of VIs. Later intercept stations were installed in the Middle East and Gibraltar.

Identifying the vast German network. Gradually about 14 separate groups covering different areas were identified. Group 2 was by far the largest and with its centre near Berlin had links (known to us as services) extending over Europe and beyond and was the mainstay of the Abwehr. We designated them as 2/141, or 8/254 for example where the group came first and then our number reference for the service. An officer, with a staff proportionate to the size of the group, was responsible for keeping the record up to date and issuing daily

amendments, as the services frequently changed and grew. When messages had been checked for mistakes and omissions, by comparison with other copies, they were sent to Bletchley Park for de-ciphering. It was important for this purpose that the 'group' was identified, for instance groups 1 and 6 were naval intelligence. Group 2 had links with other centres or sub groups such as group 5 in Prague, 7 in Vienna and 8 in Italy. Group 3 was the infamous SD under Himmler so we may guess at what some of their traffic revealed. To build up a complete picture of the enemy networks it was vital that we found the location of each transmitter. We therefore relied heavily on the nine or so direction-finding stations which were distributed as widely as possible over the UK. For more information see the Direction Finding (D/F) link. DIRECTION FINDING RSS direction finding began in 1938 when the G.P.O. created three new “U Adcock” d/f stations at Sandridge near St Albans, Stockland Bristol near Bridgwater and Cuper north of Edinburgh. They were built ostensibly as a peacetime development out of GPO’s own funds, but they were quickly formed into a military scheme by MI5 and the War Office. This was the first RSS radio activity. A concrete base still

remains at Bridgwater and the station is visible in 1946 aerial photographs. In 1942 a second station was added in an adjoining field. The original stations would have consisted of a central hut with four 10m high antennas at N,S,E&W. The feeders passed underground and came up in the centre of the hut and passed into a radio goniometer and from there to an HRO receiver. The operator received instructions from RSS HQ giving the frequency and the sound of the signal through the telephone line. This signal passed to one ear of his headphones and the other ear listened to his own receiver until he found the exact frequency. He them operated his goniometer to find a nul where the signals disappeared. He repeated this several times, took a mean of the measurements and passed it back the HQ d/f control room by telephone. The number of RSS stations quickly increased with installations at St Erth in Cornwall, Thurso on the North Coast of Scotland, Lydd in Kent and Gilnahirk in Northern Ireland. The early stations were all built and operated by the GPO an later when RSS was militarised many of the operators transferred to RSS who also recruited other operators from the Voluntary Interceptors such as Gerry Openshaw (G2BTO) who is seen below operating his d/f station in WW2.

Only a few photographs of the stations survive since they were top secret at the time and photography could have resulted in serious repercussions

SPACED LOOP D/F STATIONS

In November 1940, the then “Controller” Col. Worlledge placed an order with the GPO for seven new d/f stations of a new type called “Spaced Loop” recently developed by the National Physical Laboratory. There were designed to give much sharper bearings on transmitters at relatively short range (250 miles). The stations consisted of a rotating beam about 10m in length supporting a square loop at each end. The beam was rotated first and then a goniometer was operated to provide the final bearing. There was also another major difference, the operator was located in a large metal tank sunk into the ground directly below the aerials. While the development of experimental direction finder continued sites were chosen and metal tanks were installed at St Erth, Bridgwater, Wymondham Norfolk, Gilnahirk N.I. and Weaverthorpe Yorkshire. Of these only the Weaverthorp and Wymondham stations were installed. But by the time they were operating RSS had turned its attention to

targets operated in Europe and the Spaced Loop system was unsuitable for such distant stations. Tests at Weaverthorp and Wymndham showed the signal strengths were much reduced compared to the U Adcock stations and the Spaced Loops were abandoned by Mid-1942. In their place, RSS installed U Adcock stations keeping the underground tanks because of the protection they provided against aerial attack. One of the tanks excavated at the Clayock or Harpsdale station is shown below.

Bridgewater D/F Station 1946 2009 and Concrete Base and 4 Feeders (see inset)

Thurso D/F All the above stations mentioned were high frequency (HF or short wave) stations operating between about 2 MHz and 30Mhz but RSS also operated medium frequency d/f stations on frequencies up to 3Mz. There were of a similar design but much larger with four 30m (100ft) high guyed lattice steel aerials. John McCaffetry is shown next to the lower part of one of the aerials at the RSS M/F d/f station at Lydd.In addition to the fixed stations RSS also had a fleet of mobile d/f vans located around the UK and subsequently taken into Europe after “D” day In addition to the fixed stations RSS also had a fleet of mobile d/f vans located around the UK and subsequently taken into Europe after “D” day.

No photographs of the Spaced Loop stations have been located but the drawing below shows what they must have looked like

Although the fixed Spaced Loop stations were abandoned, mobile versions were made and used later in Europe following the Normandy invasion.

The results on the form were them plotted using a specially printed, foolscap size page, see below. It contained a map of Europe with the RSS d/f stations clearly marked and for each station there was a scale marked around the edge of the paper. The plotter would then draw the bearing from each station using its own scale finally producing a crossing point at the origin of the transmission

THE RSS TELEPHONE NETWORK

Perhaps the key to the success and speed of the operation was the telephone conference system that connected all the d/f and intercept stations with HQ using dedicated GPO lines, see diagram from the GPO archives below

DF REPORTING AND PLOTTING DF control was operated at both the Barnet HQ and Hanslope Park. The control room received bearings from the stations and recorded them on a d/f report form

RSS DF stations list of locations. Click the LINK below to see a list of RSS direction finding stations with names and locations given in Latitude Longitude. Sites are either labelled “A” or “S.L.. A refers to Adcock d/f stations and “S.L.” refers to Spaced Loop d/f stations. In fact only two of the S.L. stations were actually built (at Weaverthorpe and Wymondham). The other stations marked SL were built as Adcock stations with underground tanks described above. No evidence has been found that any station was operated from Barwinnock.

RSS and Spies

Perhaps the most spectacular accounts of RSS involvement were in connection with the spies, or agents as they came to be called, who arrived here with various

objectives. These could be used to pass information back to Germany, or carry out sabotage or, at least in the early stages, to spread rumours and alarm and despondency in an attempt to demoralize the population. Later reports on bomb damage and the range of the V bombs were required.

Among the first 21 spies to arrive in September 1940 were 4 by dinghy, 2 by parachute and some by fishing boat. In addition several arrived amongst the large number of genuine refugees, which flooded in during the German occupation of Western Europe. Among these first agents, often badly trained and prepared, were 5 Germans, 3 Cubans, 2 Danes, 2 Norwegians, 1 Swiss and 1 Belgian. Not all arrivals were enthusiastic or competent. Some gave themselves up as soon as possible and some were easily caught because of their ineptitude, but few came without our prior knowledge due to radio Morse intercepts made by our Radio Security Service. Many who tried to avoid capture and please their masters did so because their families were held as hostage. Out of some 120 illicit entries nearly 30 were made into double agents working on our behalf unknown to the enemy. They were given cover names and at least four, code-named Tate, Zigzag, Tricycle and Garbo, were of great value. Many of the others were half-hearted, perhaps coming over with refugees and not prepared for undercover work. In fact some of the deliberately infiltrated persons, by boat or air were pitifully ill-trained, with a poor knowledge of customs and language. The imperial money system of £.s.d was one stumbling block. For instance when one would-be spy was asked for 10 and 6 for a rail ticket he offered £10 and 6 shillings and was soon apprehended. Papers were often badly forged and in several cases a real give-away because ID numbers were put on documents by the Germans when these numbers had been acquired by them from our first double agent, a Welshman called Snow. Snow, real name Alfred Owens, had been in contact with the Abwehr pre-war while on business in Germany and was trusted by them. However after a while we came to doubt which side he was really on and he was interned for the duration. This was the rule with any spies who had acted for us but for various reasons we could no longer use. When the arrival was arrested and either refused to co-operate (or if the press got to know about it) he was executed. Otherwise the Germans, who might learn of his arrest, would be suspicious if he just disappeared and obviously we couldn't use the man in this case. In Wandsworth or Pentonville jails 17 were executed either by hanging or firing squad according to whether they were civilian or military. Only one arrival escaped the notice of the RSS and that was Ter Braak, a Dane, who ran out of money, and, not being able to contact his German Control, must have got so depressed that he shot himself, to be discovered in a Cambridge air-raid shelter.