The actor, who has served as a writer on the sci-fi show and created Sherlock with Doctor Who showrunner Steven Moffat, will star as The Captain in the Time Lord’s upcoming Christmas special.
Capaldi and Moffat will both depart the show after the festive episode, with Jodie Whittaker taking over as the Doctor, and Broadchurch creator Chris Chibnall replacing Moffat.
Gatiss told ITV’s Lorraine: “Earlier this year Steven said to me, ‘Will you keep the summer free because I’ve written a part for you in Peter’s last story and I want you to be there when I go’.
“We were all in tears. It was the screening the other night and we were all in tears, I’m afraid. It’s happy/sad.”
However, of the first female Doctor, Gatiss said: “It’s fantastic. What I love about this, I love the costume – I call it ‘Godspell chic’.
“It’s got a lovely early 70s feel to it, which I really like. I think it’s a fantastic choice, Jodie, it’s a whole new era.
“And I don’t know anything about it which is a position I’ve not been in since 2004. Yes (it’s strange) but it’s nice.”
Gatiss, who is well known for starring in Sherlock as Mycroft Holmes, as well as writing it, also said he does not know if there will be more episodes of the detective drama.
He told the programme: “We deliberately left it in a sort of happy place where we could go back. We have no plans at the moment. Steven and I are going to do Dracula.
“I don’t know yet (if I’ll be in it). The part I’d like is obviously Renfield, the mad man. That’s the best part. We’ll see.”
Via: The Press Office
