It's of Alan Turing, probably the most important figure in the history of Computer Science and a founding father of Artificial Intelligence. As a computer scientist with a PhD in AI, I'm naturally very enthusiastic about the current e-petition advocating his being put on the next £10 note. I can't really see its failing (especially as he came 21st in the BBC's 2002 poll, the 100 greatest Britons, beating former £20 poster boy Michael Faraday into 22nd).
I just hope that if the poll is accepted, the likeness they use for Turing is somewhat better than the one they used for that statue...