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For other uses, see MI-8 (disambiguation).

MI8, or Military Intelligence, Section 8 was a British Military Intelligence group responsible for signals intelligence and was created in 1914. It originally consisted of four sections: MI8(a), which dealt with wireless policy; MI8(b), based at the General Post Office, dealt with commercial and trade cables; MI8(c) dealt with the distribution of intelligence derived from censorship; and MI8(d), which liaised with the cable companies. During WW1 MI8 officers were posted to the cable terminals at Poldhu Point and Mullion in Cornwall and Clifden in County Gallway, continued until 1917 when the work was taken over by the Admiralty. In WW2, MI8 was responsible for the extensive War Office Y Group and briefly, for the Radio Security Service.


National HRO receiver, extensively used by the RSS

MI8 was the signals intelligence department of the War Office that ran a worldwide Y station network. For an 18-month period from late 1939 to mid 1941 it ran the Radio Security Service under the designation of MI8c. Prior to this there was the Illicit Wireless Intercept Organisation (IWIO) which was given the designation MI1g and run by Lt Col. J S Yule. From an office in Broadway, they collaborated with Military Intelligence, Section 5 (MI5) and the General Post Office (GPO) to set up and control a small network of Direction Finding (DF) and intercept stations to locate illicit transmissions inside Britain.[1] Col Yule also made detailed plans for similar networks in British territories overseas before IWIO evolved into RSS in September 1939.

At the start of World War II, Vernon Kell, the head of MI5, introduced a contingency plan to deal with the problem of illicit radio transmissions. A new body was created, the Radio Security Service (RSS), headed by Major J.P.G. Worlledge, who until 1927 had commanded a Wireless Company in Palestine. Worlledge's brief was to "intercept, locate and close down illicit wireless stations operated either by enemy agents in Great Britain or by other persons not being licensed to do so under Defence Regulations, 1939". As a security precaution, the RSS was given the cover designation of MI8(c).

Working from cells at Wormwood Scrubs, Worlledge selected Majors Sclater and Cole-Adams as his assistants and Walter Gill as his chief traffic analyst. Gill had been engaged in wireless interception in WW1 and decided that the best course of action would be to find the transmissions of the agent control stations in Germany. He recruited a research fellow from Oxford, Hugh Trevor Roper, who was fluent in German. Working alongside them at Wormwood Scrubs was MI5 and John Masterman who ran the double agent XX program. Masterman already had agent SNOW and Gill used his codes as the basis for decrypting incoming agent traffic.

Following a proposal developed by Lt Col Adrian Simpson that a small number of stations located around Britain would not work, the task of developing a comprehensive listening organization was given to Ralph Mansfield, 4th Baron Sandhurst, an enthusiastic amateur radio operator who had served with the Royal Engineers Signal Service during World War I, and had been commissioned as a Major in the Royal Corps of Signals in 1939.

Sandhurst was given an office in the Security Service's temporary accommodation in Wormwood Scrubs prison and as a first step approached the President of the Radio Society of Great Britain (RSGB), Arthur Watts, who had served as an analyst in Room 40 during World War I following the loss of a leg at Gallipoli. Watts recommended that Sandhurst recruit the entire RSGB Council, who in turn began to recruit their members as Voluntary Interceptors (VIs). Radio amateurs were considered ideal for such work because they were widely distributed across the United Kingdom.

The VIs were mostly working men of non-military age, working in their own time and using their own equipment (their transmitters had been impounded on the outbreak of war, but their receivers had not). They were ordered to ignore commercial and military traffic and to concentrate on more elusive transmissions. Each VI was given a minimum number of intercepts to make each month, which if reached gave them exemption from other duties, such as fire watching. Many VIs were issued with a special DR12 identity card, which allowed them to enter premises from which they suspected unauthorized signals were being transmitted.

RSS also established a series of Radio Direction Finding stations in the far corners of the British Isles in order to identify the locations of the transmissions they were intercepting.

The recruitment of Voluntary Interceptors (VIs) was slow since they had to be skilled, discreet, and dedicated, but within three months 50 VIs were at work and identified over 600 transmitters - all firmly on the other side of the English Channel. It became apparent that there were no enemy agents transmitting from the UK - in fact, all German agents entering the UK were promptly captured and either interned or "turned" to operate as double agents under the supervision of the "XX Committee". In some cases, a British operator took over their transmissions and was accepted by the Germans as one of their agents.

Move to Arkley[edit]

Initially the messages logged by the VIs were sent to Wormwood Scrubs, but as the volume became so great, and Wormwood began to suffer German air attacks, the decision was made to seek larger premises. Arkley View, a large country house near the village of Arkley, in the London Borough of Barnet, had already been requisitioned as an intercept station, and it was decided to move to this locale, which was given the cryptic postal address of Box 25, Barnet.[2]

There a staff of analysts and cryptographers began their duties and by May 1940 it was clear that RSS's initial mission - to locate enemy agents in the UK - was complete.

MI6 takeover[edit]

RSS had in effect become the civilian counterpart of the military's "Y Service" intercept network. By mid-1941 up to 10,000 logs (message sheets) a day were sent to Arkley before being forwarded to the code-breaking centre at Bletchley Park. The success of the RSS, and the fact that some of its personnel had managed to decode some Abwehr cyphers ahead of Bletchley, meant that control of the organization was transferred to Military Intelligence, Section 6 (MI6) in May 1941 after some conflict over exactly which department should control it.

The new controller of RSS was Lieutenant-Colonel E.F. Maltby, and from 1942 Lt. Col. Kenneth Morton Evans was appointed Deputy Controller and Roland Keen, author of "Wireless Direction Finding", was the officer in charge of the engineering. Well-financed, and equipped with a new central radio station at Hanslope Park in Buckinghamshire (designated Special Communications Unit No.3 or SCU3), it became the communication and interception service of MI6 which previously had possessed no such capability. The Abwehr was now monitored round the clock and the volume and regularity of the material obtained enabled Bletchley to achieve one of its great triumphs in December 1941, when it decoded the Abwehr's Enigma cypher, giving enormous insight into German intelligence operations.

At its peak in 1943-1944 RSS employed - apart from VIs - more than 1,500 personnel, most of whom had been amateur radio operators. Over half of these worked as interceptors while a further number investigated the numerous enemy radio networks. This revealed important information, even when it was not possible to decode messages. Few transmissions by secret agents of German Intelligence evaded RSS' notice and changes in procedure, which the Germans used for security, were in many cases identified before the enemy had become familiar with them.

Following the end of the war RSS HQ moved to Eastcote and was absorbed by the Government Communications Headquarters (GCHQ).

Wilton Scheme[edit]

The "Wilton Scheme" was operated briefly from March to May 1945. It was feared that British Prisoners of War might be used as hostages by the Germans, and attempts were made to make radio contact with the prisoners to get information about such a situation if it developed. In various POW camps, radio amateurs and signals officers had constructed radio receivers and in some cases transmitters (kept for emergency use). They had been kept informed of the war news. However, no contact was made.[citation needed]


  1. ^ TNA File WO 5/208
  2. ^ "Box 25" (PDF). The RSS from 1939 to 1946. Retrieved 19 March 2013. 

Further reading[edit]

  • West, Nigel. GCHQ: The Secret Wireless War 1900-1986. Hodder & Stoughton. ISBN 0-340-41197-X. 
  • Geoffrey Pidgeon (2003). The Secret Wireless War: The story of MI6 Communications 1939-1945. UPSO Ltd. ISBN 1-84375-252-2.