William Hartnell: No-one knew the show was going to run for fifty years- and Hartnell- who had spent his career playing toughies (he was Richard Attenborough's side-kick in Brighton Rock) turned in a mannered performance as a crotchety grand-dad. In some ways it was a false start, but it established the Doctor as an odd, ambiguous cove and ensured that- no matter how young and dashing his later incarnations- he was never going to dwindle into a big-chinned space explorer.
Patrick Troughton: Troughton's other TV work has been forgotten (probably wiped) but he was one of the BBC's first big stars. I remember watching him play St Paul and Quilp in Saturday afternoon drama serials. His Doctor was playful, fey, lovable and did a lot of running away.
John Pertwee: Pertwee was a second tier comedy actor- one of a host of radio names who wasn't Sellers or Milligan or Hancock. Dr Who gave him the chance to do something completely different and he later spoke of finding himself in the role. He was the first Doctor who could hold his own in a fight, also the first to have a driving license. I seem to remember watching an episode that consisted largely of Pertwee dashing about in a hovercraft.
Tom Baker: I've no idea where they found Tom Baker. A bona fide eccentric, he threw played himsef into the role and has never done anything memorable since. He remains the definitive Doctor, not the best, but the one the cartoonists reach for when they want to picture the character in its essence.
Peter Davison: Davison turned down the volume and played the Doctor as a quirky, cricket loving, older brotherly type. He's the Doctor it's least easy to caricature- in spite of the leek, the one who best resembles a regular chap. For the earlier actors the role was a pinnacle, for Davison it was just an episode in a long and distinguished TV career.
Colin Baker: Oh dear. Did they cast him for his surname? To be fair Baker planned a character arc which would have seen his Doctor soften and mellow but was cut off before his prime
Sylvester McCoy: Previously known as the chap who stuck ferrets down his trousers on the Ken Campbell Roadshow, McCoy gets a bum rap. He's primarily a clown- but then so was Buster Keaton. If The Curse of Fenric isn't the best story ever I'd like to know what is.
Paul McGann: The first sexy Doctor. He'd have been really good if given a chance, but the attempt to reinvent the character as an action hero in the American style was ill-conceived and quite rightly died the death.
(John Hurt: Oh those sad, sad eyes.)
Christopher Eccleston: The revived show could afford the best. Eccleston was an odd choice and an odd fit but, hey, every planet has a north.
David Tennant; Tennant brought an unprecedented emotional breadth to the role and was indulged- possibly over-indulged by the writers. Put it this way: no other Doctor has also been a star of the RSC and the definitive Hamlet of his generation.
Matt Smith: A relative unknown (though not any longer.) Lightweight but genuinely funny. Also as alien as they come.
Peter Capaldi: Promising...