Sidney Reilly would probably be the closest fit, he was an Agent of the Secret Intelligence Service throughout World War One and into the Russian civil war. He was executed after being captured by OGPU agents in 1925 after attempting to contact "The Trust", ostensibly a White Russian resistance movement but in reality a front for the Joint State Political Directorate (OGPU).

You can find an account of his exploits under C's direction in Keith Jefferies the secret history of MI6 which is the Secret Intelligence Services official public history.

If you want further reading the defence of the realm which is the Security Service's (MI5) official history is also good reading.

Edit: Forgot to add, he was also one of Ian Fleming's role models for Bond.