Most of the books I’ve read claim that all those efforts resulted in failure and no important sources of information were available. However I noticed that in the book ‘Spycatcher: The Candid Autobiography of a Senior Intelligence Officer’ by Peter Wright (former Assistant Director of MI5) there is mention of a spy in the Kremlin.In Chapter 15, p220 we get:
I switched back, and began to press his conscience. "Have you ever thought about the people who died?" Blunt feigned ignorance. "There were no deaths," he said smoothly, "I never had access to that type of thing . . ." "What about Gibby's spy?" I flashed, referring to an agent run inside the Kremlin by an MI6 officer named Harold Gibson. "Gibby's spy" provided MI6 with Politburo documents before the war, until he was betrayed by Blunt and subsequently executed. "He was a spy," said Blunt harshly, momentarily dropping his guard to reveal the KGB professional. "He knew the game; he knew the risks."
Who was this spy? What information did he give his controller and how did Blunt compromise him? Gibson was a longtime MI6 officer who served in Turkey and Czechoslovakia but I haven’t been able to find more information on his agent.This spy must have been the person mentioned by Walter Krivitsky when he was interrogated by the British. Krivitsky was head of the Red Army’s foreign military intelligence network in Europe in the 1930’s but he defected and managed to get to the US. There he publicly attacked Stalin in a series of articles and in 1940 visited the UK and was interrogated by the British authorities. These reports refer to him as ‘mr Walter Thomas’.
In one of these he mentions how his chief Slutsky called him sometime in 1937 and showed him information from one of their spies in Britain. This person gave the Soviets copies of the proceedings of the Committee of Imperial Defense . One of these documents had information from a Politburo meeting that clearly showed that the British had a high level agent.
I assume that this person was ‘Gibby's spy’.