For readers of classics like The Making of the Atomic Bomb and the more recent histories like Code Girls who want stories about the tech behind military success and the small maverick groups that generate historic innovations

This is a previously classified story of one group of scientific researchers—men and women—who exposed themselves to extraordinary risks to make D-Day a success.

On the beaches of Normandy in France two summers before D-Day on June 6 1944, the Allies attempted an all but forgotten invasion. Of the nearly 7000 allied troops sent ashore, only a few hundred survived an unbelievably terrible massacre. The reason for the debacle was a lack of reconnaissance. Was the beach sand firm enough for tanks? How shallow was the offshore water? How soft and steep were the surrounding cliffs? How deadly were the fortifications? The Allies knew they could not afford another disaster like that. The emerging technology of mini-submarines was already being pursued in the Pacific by the Japanese and in the Mediterranean by the Italians. But a small group of extremely eccentric scientists, researching in pressure tanks in the middle of the London Blitz air raids, would devise the critical reconnaissance vessels that would enable the Allies dramatic, history-making success on D-Day.

Based on secret documents only recently declassified and hunted down in England by Rachel Lance, this is the story of a band of maverick, hard-drinking submarine researchers, led by the controversial, brilliant biologist and communist sympathizer JBS Haldane and the intrepid, courageous Dr. Helen Spurway. Who fell in love...