The great betrayer

When Klaus Fuchs started passing atomic secrets to the KGB, he changed the course of world events. Forget about Philby and the Cambridge Five, that preening group of loudmouths that still dominate our national history of Soviet treachery. In his own quiet, devastating way, Fuchs proved more significant than all of them put together.

A brilliant but unassuming German refugee who found sanctuary in Britain, Fuchs rose to become one of the leading theoretical physicists of the Allied nuclear bomb project. As Frank Close, himself an Oxford nuclear physicist, writes: ‘By 1946, Fuchs knew more about the construction of the atomic bomb and the conception of the hydrogen bomb than anyone in the UK and all but a handful in the world.’ And because Fuchs knew it, his KGB handlers knew it too. Judging by this engrossing, brilliantly researched book, they knew it all.

Born in 1911 in Germany, Fuchs was a gifted, socially reticent man.