James Klugmann was born in 1912 into a prosperous and liberal north London Jewish family. Precociously bright, he went on to read history at Cambridge in the 1930s, after which a successful academic career seemed to beckon. Instead, he committed himself to the Communist Party and spent the rest of his life working for it as an organiser, educator, proselytiser, historian, editor and talent spotter. He died in 1977, largely unknown beyond the confines of the Party and MI5, which had monitored his career since 1934. So, why a biography?