In the shocked aftermath of Hiroshima and Nagasaki, Clement Attlee realised at once that -the nature of security and strength in the world had changed irrevocably. He ordered a superhuman effort to make Britain a nuclear power. Although Britain had been a junior partner in the Manhattan Project which had produced the American bombs, no British scientist had more than partial knowledge of the complex physics involved. The war over, the United States cut off all help. At a time of daunting economic difficulty and amid the growing tension of the Cold War, the project hurriedly took shape behind a cloak of almost paranoid secrecy and in an atmosphere of constant stringency and shortage. Brian Cathcart's book ranges over politics, diplomacy, espionage and science, but above all it tells the story of the brilliant young scientist William Penney, his team and their struggle. For the first time the men who worked behind the security fences at Aldermaston have been allowed to speak. The tale includes fearsome risks, Heath Robinson resourcefulness, bureaucratic obstruction, naval intransigence and a measure of black humour. The veil is also lifted on the extraordinary contribution of Klaus Fuchs, the Soviet spy. Finally the high drama of the test itself, conducted off the coast of Australia after a naval operation which came close to total fiasco, is recounted.