MI8 MI8 , or " Military Intelligence , Section 8 " , was the cover designation for the Radio Security Service ( RSS ) , a department of the British Directorate of Military Intelligence , part of the War Office . It was a British signals intelligence group in World War II . History . 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 . 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 . 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 . 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 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 . 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 .