A lot of people are turning up at the blog seeking an answer to this question.
The answer, as far as I know, is that he is not. Neither are any of the other Doctors to the best of my knowledge, though I'd guess Colin is the most likely of all of them to take the plunge.
Some other Doctor Who types who are on Twitter include Murray Gold, Sheridan Smith, Noel Clarke, Neil Gaiman, Jason Arnopp and Paul Cornell.
I've compile a list below of some types you might want to follow.
Doctor Who types on Twitter
• Ben Cook
Feel free to suggest any I've missed.
Peter Davison couldn't make the Gallifrey One convention this year, he's starring in the Legally Blonde musical alongside Sheridan Smith, but he sent this remote message by way of greeting.
Davison, who was My Doctor as it goes, shows his comic skills off and a willingness to send himself up that has served him well through his career. There's also a very Doctorish moment at 4.10 to look out for.
And if you think that's good, wait until the very end.
And here's another little vignette of Peter being amusing in The Kidnappers, along with Mark Gatiss and David Walliams from BBC2's Doctor Who night which, startlingly, was over ten years ago.
"Do you think it would be alright to... kiss Peter Davison?"