Dexter Fortescue was a red-nosed, corpulent wizard who was at one time a Headmaster of Hogwarts. His portrait hangs in the Headmaster’s office (OP27).
Possibly related to Florean Fortescue. -BB
The red nose is an interesting detail. Perhaps he had a cold when he sat for his portrait. But heavy drinking can also cause one to have a red nose. -BB