Hi there! In this morning's Internet edition of the (London) Daily Telegraph there's an obituary of a woman named Madeau, surname Stewart; described as having been born in 1922 to an English father and a French mother. No other given names are recorded, and the DT is usually most meticulous in doing so if they exist.
Any ideas? The best I can come up with is a blend of Madeleine and Isabeau, but it's quite a stretch and seems unEnglish as well as unFrench.