Churchill's Bolshevik cousin was Soviet informer

Sir Winston Churchill's cousin was a Bolshevik sympathiser who passed details of conversations with him to Soviet agents, documents released today show.

Clare Sheridan also passed on conversations with Churchill and other politicians to William Ewer, who was a key figure in Soviet intelligence-gathering in London in the 1920s.

MI5 viewed her as a "consistently anti-British" person who should be treated with "extreme caution". In 1925, MI5 interviewed Churchill, then Chancellor of the Exchequer, about his cousin.

A record of the interview released by the Public Record Office states that Churchill would not defend his cousin and was prepared to take action against her if asked.

"Winston informed him [the interviewer], in answer to his question as to what he thought about Clare, that he was not prepared to go bail for her, in fact he was prepared to believe anything ... told him about her," it said.

The interview followed intercepted telephone calls from Ewer, who was foreign editor of the Daily Herald, in which he relayed remarks made earlier by Sheridan. These were summarised as: "Winston [said it] was not certain that the French could hold in Syria."

Another document includes details of conversations between two Russian agents which showed she had given one of them the same information.

Sheridan, who was related to Churchill through her American mother, was born in London in 1885 and became a sculptor, writer and traveller. She was invited to Moscow in 1920, where she made busts of Zinoviev, Lenin and Trotsky but found herself ostracised when she returned to London.

MI5 recorded that she "preached Bolshevism" in Rome in 1922, and two years later, her files state, she "conducted herself in a disloyal manner in various foreign countries, adopting a consistently anti-British attitude".

She was still being monitored in 1942 when agents intercepted a letter to an acquaintance known as "Alice" in New York.

It showed Sheridan had advance knowledge of when Churchill, who by then was Prime Minister, would be leaving Washington.