John Beckett was a rising political star. Elected as Labour's youngest M.P. in 1924, he was constantly in the news and tipped for greatness.
But ten years later he was propaganda chief for Mosley's fascists, and one of Britain's three best known anti-Semites.
Yet his mother, whom he loved, was a Jew. Her ancestors were Solomons, Isaacs and Jacobsons, originally from Prussia.
He successfully hid his Jewish ancestry all his life - he said his mother's family were "fisher folk from the east coast." His son, the author of this book, acclaimed political biographer and journalist Francis Beckett, did not discover the truth until John Beckett had been dead for years.
He left Mosley and founded the National Socialist League with William Joyce, later Lord Haw Haw, and spent the war years in prison, considered a danger to the war effort.
For the rest of his life, and all of Francis Beckett's childhood, John Beckett and his family were closely watched by the security services. Their devious machinations, traced in records only recently released, damaged chiefly his young family.
This is a fascinating and brutally honest account of a troubled man in turbulent times.