Manning Coles was actually two people, Cyril Henry Coles and Adelaide Oke Manning. "Drink to Yesterday" was the first in a series of spy stories, and is based in part on Coles' experiences in WWI. It and the sequel, "A Toast to Tomorrow", are fairly realistic; from then on the stories get fluffier, but I still found them amusing when I read them a lifetime ago. "A Toast to Tomorrow" presented a good picture of Germany between the wars, useful to me as background.