As Gill Bennett relates in this superb book, a compelling mixture of history, anecdote and historiography, the Zinoviev Letter arrived in Britain in 1924 and has never really gone away. Three weeks before the general election of October that year, a decoded telegram reached the headquarters of Secret Intelligence Service (SIS) in a villa in Holland Park from its Riga station. It purported to be a translation into English of a communication from Grigori Zinoviev, the Bolsheviks’ propaganda chief, to the Communist Party of Great Britain (CPGB). Zinoviev was head of the Comintern and had in that capacity written a number of letters to European communist parties urging them to radicalise the working classes in their countries. The letter that had allegedly been sent to the CPGB, signed also by a Finnish communist, Otto Kuusinen, and by Arthur MacManus, a Clydeside docker, claimed that the re-election of a Labour government would confirm the stability of diplomatic relations between the two countries (which Labour had instituted in January 1924 but which would be under threat if the Conservatives won) and stated that closer contact between the two countries would facilitate the spread of Leninist propaganda and ideals in Britain.

The letter did not say that a Labour government would be the useful idiot of the Bolsheviks, but that was its implication. It also scolded the CPGB for inadequacy in its programme of agitation, especially in encouraging radicalisation within the armed forces. Major Desmond Morton, the SIS officer on whose