The Abwehr is usually the butt of jokes on WWII intelligence .lt is claimed that all their agents were caught and turned, they had no good sources etc. etc.
Victors get to write history, always have always will but occasionally some embarrassing details slip out.
This case concerns a Russian émigré named Von Petrov who worked at the same time for two intelligence agencies. The Soviet GRU and the German Abwehr. In reality he was only loyal to the Russians but he did provide the Germans with very valuable information.
Vladimir Von Petrov was a White Russian émigré based in Paris.He was an agent of the GRU with good sources in Britain and Germany.
The Germans ran Petrov without knowing of his connection to the Russians. His spy in MI6 was a Captain Ellis (Charles Howard ‘Dick’ Ellis).Thanks to him, Petrov provided the Abwehr with the MI6 order of battle plus details of important operations such as the tapping of the telephone link between Hitler and the German Ambassador (and later Foreign Minister) von Ribbentrop.
Elli’s last contact with the Russian émigrés was in December 1939.
Source for all the above information: Spycatcher ,p325-330
Also from ‘Encyclopedia of Cold War espionage, spies, and secret operations’ by R. C. S. Trahai, p71
Early in 1966 the FLUENCY Committee, a joint MIS-M16 high-level investigating group, sought reliable knowledge of Soviet penetration in Britain's security service and SIS. It investigated Ellis to discover if he might have been a Soviet spy. The committee concluded Ellis had been a paid agent of the Germans up to 1940, and that he might have served the Soviets from as early as 1920. To test their conclusions, the committee need a confession from him. Aged 71, Ellis was brought in for interrogation. He denied spying for Germans and Russia; later he admitted he had helped the Germans in the 1939 Venlo Incident, and had given information to the Russians in 1939.
Finally from ‘Historical Dictionary of British Intelligence’ by Nigel West , p49
It was only much later that SIS learned that another SIS officer, Dick Ellis, had spilled secrets to the Abwehr before the war, and this was the information that was presented to Best and Stevens separately for corroboration during their incarceration. Each assumed the other had been responsible for supplying the information, little realizing that it had been neither. Ellis confessed to his treachery, citing financial hardship as a motive, only in 1966.
This case shows the long reach of Soviet intelligence. So the question is why did the Russians allow von Petrov to compromise MI6 so badly?