Why Every Lead Actor Left Doctor Who

Peter Capaldi actually played two other characters in the Whoniverse before he was cast as the main attraction: Caecilius in 2008's The Fires of Pompeii, and John Frobisher in Torchwood: Children of Earth. Rather than these past lives being ignored during the Twelfth Doctor's reign, this identity crisis formed a core part of his arc.

Despite ratings dipping from the Tennant and Smith eras, Capaldi enjoyed three strong series in the role before regenerating in the 2017 Christmas special. This was actually a last-minute adjustment, with the original plan being for him to bow out at the end of Series 10 in July.

As for why he left? Again, this was another case of the actor deciding to call it quits. Though incoming showrunner Chris Chibnall did try and persuade him to stay – and Capaldi considered it – he opted out, saying that he wanted to leave while he was still enjoying it.

He's also indicated that the workload was a factor. In 2018, he candidly stated:

"To be at the centre of that brand is a lot of work. It was hard to maintain that level of commitment with that schedule any longer. I tried my best to make the Doctor come alive.”

This might explain why he's not so keen on a return. His response when asked about the possibility? A simple "No."

Fingers crossed he changes his mind in future!