Can you help me identify this man?

My English grandmother had this among her own paintings. It isn't hers, I don't think. She did mostly charcoal and wash and while her landscapes were lovely, I fear she often ruined them by sticking in rather wooden little figures.(Sorry about that, Grandmother, but I still love your poppies).
So there are two questions:
Who did do this? It is more a sketch than a painting. I love the fast, fat brushstrokes and brief lines that caught the expression so well but there is no signature or clue to the artist
Who is that dapper man? He was probably in England, perhaps 1940 - 1960s. Could he be the Jamaican aircraft engineer that made friends with my father when working together at a (Rolls Royce?) factory, just after WWII? What happened to him?
Well, perhaps there is another question for me - Why did my English grandmother have this in her possession?