The job required precision. “It was drummed into us that we must be accurate otherwise a lot of very important work by very clever people would be ruined,” she said. Like her colleagues, she had no idea of the bigger picture. “I never even heard the name Enigma until long after the war,” she said. “I was just putting wheels on and taking them off and putting plugs in and so on.” The work was intense and the shift rotation exhausting. Eventually Henry collapsed and her mother was summoned. “Being a good Jewish mother, she brought me half a cooked...