M. Hercule Flambeau first appeared in G. K. Chesterton's novels as who?

M. Hercule Flambeau is a fictional character created by English novelist G. K. Chesterton, who appears in 48 short stories about the character Father Brown. A master criminal, his surname "Flambeau" is an alias, the French word for a flaming torch.

He first appeared in the story "The Blue Cross" as a jewel thief. Father Brown foiled his attempted crimes in this and several other stories. As a notorious and elusive criminal, Flambeau is a worry for law-enforcers. He is exposed by Father Brown, and later becomes a detective himself. His last appearance as a thief occurs in "The Flying Stars", in which Father Brown persuades him to return his loot and to give up the criminal life. As a reformed criminal, Flambeau assists Father Brown in a number of other short stories, beginning with "The Invisible Man".