His major discovery in the years leading up to the war was the singer Vera Lynn, who sang with his band from 1937 to 1940 and, during the war, became known as the "Forces' Sweetheart". Lynn married Harry Lewis, a clarinettist in the band, in 1939. Other singers with the Ambrose band included Sam Browne, Elsie Carlisle, Denny Dennis, who recorded a number of duets with Vera Lynn, Max Bacon (also the band's drummer), Evelyn Dall and Anne Shelton, with whom "When That Man is Dead and Gone", a jibe at Adolf Hitler, written by Irving Berlin, was recorded in 1941. Ambrose's signature tune was "When Day is Done".