The Eleventh Doctor made no secrets that he would love to settle down and become the Curator at the Gallery near the Tower of London. According to the man in charge currently, he might just do that. Tom Baker guest starred as the Curator, and while it was never implicitly stated, it is heavily implied that he is an older form of the Fourth Doctor, the face revisited after the Doctor finally does retire. He hints that Gallifrey did indeed survive and that it will eventually be located. Tom Baker was the only Classic Who Doctor to make a guest appearance in the 50th anniversary special. If they were only allowed to pick one, they definitely made the right choice!