Simple rules...

1. Guess who it is, the first person to get it posts the next picture, post your guess as a reply to this thread.
2. Wait for the person who posted the picture to confirm that you are correct before posting a new picture.
3. If the person who posted the picture does not answer the guesses for 48 hours, I will award the next turn to someone else, or post a new picture.
4. NO OBSCENE PICTURES. As with anywhere else in these forums the result will be an immediate ban.
5. Pictures do not need to be Unix/Computing related.
6. If you guess correctly you may 'pass' on your turn to post a picture by posting to say you are passing, the previous poster may then post another picture.

First one to get started.

Alan Turing

Here's one:
EDIT: Ack! Got ahead of myself, I'll wait for confirmation

Correct...go ahead.

Time for a hint maybe:

He is (or was) a physicist

Richard Feynman?

No, but they were contemporaries.

Hint #2:
Feynman is American, whereas the person in question is British.