Hindroth deserves a mention since he certainly held a Communist Party card, even though he was a spy for the British state who penetrated the Party during the Second World War.
A journalist, recruited to work for MI5, he became the secretary of the Workers’ Music Association. This was because the security force wholly wrongly suspected the Communist Party (or claimed it suspected it) of a plan to use the WMA as a cover force within the wider armed forces, in the event of a break down of state control and in the advent revolution. Seemingly, the aim would have been to use the WMA as means of maintaining covert contact with Party members in the armed forces, by using a seemingly innocent cultural organisation.
Hindroth’s cover name in the Party was Ian MacKay but he could not have been a very good agent since he was suspected even at the time of being a spy by Robbie Robson (see separate entry).
It is one of those uncertainties of history that we will never know if the reason for the fact that the WMA never did become a major front for the organisation of soldiers was because this was never the intention of the Party (which would certainly chime with its enthusiasm for the war after the invasion of the USSR), or because Robson’s nose for entrists alerted him to Hindroth’s role. Perhaps posterity knows the answer? But MI5 refuses to accept it, since an entirely uncritical account of Hindroth’s role has been released by the secret body.