In 1950, as the reality of Cold War was beginning to sink in to an exhausted post-war Britain, scientists at Harwell in Oxfordshire were working on Britain’s nuclear programme. Its scientists along with American allies had proved the devastating practical application of atomic research five years earlier in Hiroshima and Nagasaki. In 1950, one of its most brilliant researchers, Bruno Ponticorvo left his Abingdon home with his family ostensibly for a holiday in his native Italy and then vanished completely only to reappear five years later in Moscow.

Frank Close is a celebrated physicist himself and a resident of Abingdon and has long taken a keen interest in the case. Was Ponticorvo a spy? He weighs the evidence, chases down ‘lost’ MI5 documents, speaks to friends and family and concludes that it is the likeliest explanation.

But he does much more than this in a book that explains to the layman the principles behind building a nuclear bomb at a time when the atomic nucleus was not fully understood. He retells the story of the quest to get heavy water - a key component of nuclear reactors - out of French laboratories after the country’s fall to the Nazis. He looks at Ponticorvo’s research in the United States and in England for which his contemporaries built on his insights to win Nobel prizes while on the other side of the Iron Curtain, Ponticorvo did his science under close Soviet guard.

Close has a rare ability among science writers to contextualise the research within the wider political realities it was taking place - and his sleuthing clearly comes as a result of persistence and old fashioned shoe-leather reporting. It makes for an excellent read.