The fourth (and arguably the all-time most popular) Doctor, Tom Baker, said in an interview that, contrary to official statements, he will be appearing in this Saturday’s 50th anniversary Doctor Who special, ‘The Day of the Doctor.’ Here’s the quote:
I am in the special. I’m not supposed to tell you that, but I tell you that very willingly and specifically; the BBC told me not to tell anybody but I’m telling you straightaway.
Seems pretty cut and dried, unless he’s lying. Which he might be.