Intelligence Officers' Small Talk: Tiltman Meets Liddell

 

Guy Liddell, the Director of Counter-Espionage in MI5 during the Second World War (and beyond) kept a diary – in fact he dictated an account of each day's activity which was typed up. The diaries from 1939 to 1953 have been released to The National Archives: they are an important resource for anybody interested in UK intelligence history. The entry for 24 October 1944 (TNA reference KV 4/195) recounts a conversation with John Tiltman, the "Chief Cryptographer" at GC&CS, what today would be called the Head of Cryptanalysis. They had each been appointed CBE in the 1944 New Year's Honours List and attended their investiture on 24 October.

"I attended the investiture at Buckingham Palace where I met Tiltman of GC&CS. Tiltman reminded me of the time when he and I had gone down to some firm in Southampton Row to inspect a holorith [sic] machine. This was a good many years before the war. He said he had no idea at that time that the holorith was going to be such a big factor in the work that he would be doing. He did not know what future there would be for GC&CS but he could not help thinking that the difficulties of the work might become insuperable when foreign govts. realised the mistakes that they had made during the war. Intelligence might well be driven back on the old cloak and dagger lines. Tiltman is now Chief Officer on cryptography and a Brigadier. He said that this does not prevent him from a certain amount of daily exercise in his special line without which he thinks his usefulness to the organisation would disappear in a very short time. He says that methods change so quickly that it is absolutely essential to do a certain amount of hack work, otherwise one's usefulness will entirely disappear."

There were very few contacts between GC&CS and MI5, even on operational matters: all communication was expected to go through SIS, and SIS decided what each needed to know about the other. This is the only record, I believe, of Tiltman dealing with a member of MI5 during the war and the conversation, as recorded by Liddell, looks like the sort of small talk two senior members of different agencies might exchange at such an event. But effectively Tiltman says only three things, and doesn't really tell Liddell anything.

Hollerith machines were extremely important at Bletchley Park, as they had been in Room 40, as a means of sorting and analysing information, but they were not the sharp end of Bletchley's information technology. By this time Bletchley's cryptanalytic work was being supported by some 200 Bombes (as well as sharing time on US Bombes) and by 5 Colossus machines (a sixth would come into service four days later). It is instructive that Liddell obviously got no sense of this.

The statement that cryptanalysis might become impossible once foreign governments became aware of the mistakes they had made and that therefore Humint would become dominant is superficially plausible but it begs the question of how they were going to find out. Sigint security had developed into a sophisticated process during the war, with even the fact of interception of enemy communications not being discussed publicly. The Ultra dissemination system was designed to restrict knowledge of the fact of successful cryptanalysis of enemy communications to an absolute minimum, while an equally sophisticated process allowed action to be taken on Ultra intelligence by finding plausible alternative sources for it. The success of the US attack on Japanese encryption would become known during the Pearl Harbor enquiry, but that was a year after this conversation.

Tiltman's views about the need to keep his hand in if he is to remain useful to GC&CS is uncontentious, though I imagine he really meant that he enjoyed any opportunity to be a cryptanalyst instead of an administrator.

The main surprise to me in this conversation is that the subject of signal security didn't come up. At this time MI5 was trying to establish itself as lead department in this field even though it controlled none of the assets required either to monitor UK service or civilian traffic or to secure communications. A Wireless Telegraphy Security Committee had been in existence since 1941 but MI5 had never been a member, and MI5 raised the subject at the JIC – which GC&CS wasn't a member of. Liddell's diaries show that MI5 was not impressed by the Radio Security Service, whose job was to intercept and process illicit signals (messages sent by unauthorised individuals using radios) and which was controlled by SIS. (It would become part of GCHQ after the war for a short period before its functions became part of GCHQ normal business.) Reading Liddell's diaries, it feels to me that MI5's instinct was that signal security was part of national security, and therefore MI5's business, even if it had no realistic way of securing signals.

This is a really frustrating extract: there was so much that Liddell and Tiltman could have talked about, but they didn't. Two senior members of two secret agencies recognised each other at a formal state occasion and exchanged pleasantries, but nothing else.