The secrets that might save a nation could shatter a marriage. Madly in love, Diana Foyle and Brent Somerville married in London as the bombs of World War II dropped on their beloved city. Without time for a honeymoon, the couple spent the next four years apart. Diana, an architectural historian, took a top-secret intelligence post at Bletchley Park. Brent, a professor of theology at King's College, believed his wife was...