"A Matter of High Policy"

Harold Charles 'Ken' Kenworthy is one of the less well-known of the technical experts of Second World War Sigint. He was Head of the Metropolitan Police Sigint unit when he became part of GC&CS in 1939, asked to oversee the work of the GPO operators at Brora, Cupar and Sandridge as well as that of his operators. He became Head of the GC&CS Research Station at Knockholt which took German teleprinter traffic. He designed the original 'Tunny' machine to process enciphered teleprinter signals. He progressed in GC&CS during the war, and continued to work in GCHQ afterwards.

Even less known is the story of how he came to be employed by the Police. He had become interested in Sigint when, as a Lieutenant RNVR, he was Port Wireless Operator at Gibraltar during the First World War. He carried out interception of Spanish government traffic to prove that it was they who were deliberately jamming British reporting of enemy submarine traffic, and developed the first British D/F network in the Mediterranean to focus on Austrian submarine traffic. After the war, he took up a post with the Marconi company. In 1922 he went with a party from Marconi to India: he demonstrated the state of the art in High Speed Working to the Indian PTT which immediately placed a large order for the equipment. Kenworthy was therefore moved on to help demonstrate transportable radio telephony to the Indian authorities, and set up and carried out successful experiments designed to show that radio telephones could be operated from moving vehicles. On his return to the UK he demonstrated this capability to Scotland Yard in January 1923, and when the Metropolitan Police ordered this equipment for their vehicles, Kenworthy was loaned to them by Marconi, a loan which eventually became a transfer. By 1926 he was Head of the Met's Sigint Station which was based at Scotland Yard until 1936. 

He wrote a short memoir of his Sigint service in 1957 when he retired which is now in TNA in Kew (in HW 3/81). One of the stories he tells is of illicit wireless usage during the 1926 General Strike which was exposed by innovative technical equipment he designed pretty well on the fly and which might have resulted in acute public embarrassment for a certain party had not 'higher policy' intervened to keep the matter secret. Now read on …

"During the years 1923 to 1926 a certain amount of interest was taken in the use of short wave and out of petty cash an experimental transmitter and one or two receivers were gradually constructed. It was on one of the latter that the first strange unknown signal was intercepted which had a direct bearing on future Foreign Office interception. It occurred on the first day of the General Strike in 1926 when one of the PC operators reported a station on short wave with a very strong generator hum using a German call sign 'ABA'. At least it appeared to be German but several things were observed. Firstly Berne three letter call sign allocations for Germany had not passed AD; secondly the station was so strong (from Scotland Yard) that a local station was suspected. Thirdly, it was assumed that as it was apparently working in London and using a false call sign, it must be unauthorised. Immediate contact was made to the Assistant Commissioner Special Branch Sir Wyndham B Childs. The Assistant Commissioner rang up Chief SIS with the result that a Col Peel arrived shortly with Mr L P Lambert [Wireless Technical Expert of GC&CS]. As soon as they were convinced of our reliability as communication personnel they agreed that we should endeavour to locate this station as it appeared to belong to a subversive organisation having some bearing on the General Strike. For some reason best known to SIS and Assistant Commissioner it was decided that the problem should be tackled by ourselves without calling in the GPO. To this end Mr G M Wright and Mr S B Smith, both well versed in DF practice were asked to co-operate and the Marconi Company set about improvising two mobile DF installations and installing the apparatus in Crossley Tenders loaned by the police. This work took time but in the meanwhile the author [i.e. Kenworthy] made a portable DF set and put it in a Gladstone bag. During this period all transmissions were being logged even to the number of callsigns. The signals which were being passed made it clear that other stations were being set up.

The portable set was put to good use. Influence by Assistant Commissioner and SIS made it possible to get access to roofs of buildings in the vicinity of the suspected source of signal which had been roughly located by taking a completely empty van and sitting on the floor with the Gladstone Bag. It was as well that this small piece of apparatus had been made because the two vans fitted by Marconi proved to be wash-outs owing to reflections from buildings making 'cuts' impossible. It was gratifying that the work put in by the Wireless Telegraphy staff of Scotland Yard and Mr Lambert was finally rewarded by actually 'walking in' from the roof tops into the top floor of a building housing the transmitter whilst the operator was using it. The result was an anticlimax as the transmitter had been set up by the Daily Mail, who thinking that Post and Telegraph personnel would be joining the strike at any moment decided to try and be ready for a 'coup'. The call sign ABA was derived from Alfred Harmsworth. As a matter of high policy nothing was ever published of this exploit."