His episode has been described as an "intergalactic gargantuan extravaganza".
Kadiff Kirwan is swapping Slow Horses' dingy Slough House for the Whoniverse, as he has joined the cast of Doctor Who season 15.
While not much is known about Kirwan's character, the BBC has revealed that he encounters the Doctor (Ncuti Gatwa) and new companion Belinda Chandra (Varada Sethu) for an "intergalactic escapade" – and given this is Doctor Who, that could be anything!
Kirwan has starred in a number of acclaimed TV shows over the years, first appearing in Michaela Coel's Chewing Gum and BBC Three sitcom Crims, and going on to star in Black Mirror, Fleabag, I May Destroy You and This Is Going to Hurt.
"I feel elated to be joining the rich legacy of actors who have guest-starred in Doctor Who," said Kirwan.
"Russell T Davies and [writer] Juno Dawson have truly outdone themselves with this episode in what I can only describe as an intergalactic gargantuan extravaganza. It’s packed with gravity-defying mastery beyond imagination, and being a part of it is an absolute dream. Strap in Whovians, this one is gonna rock your world!"
Showrunner Russell T Davies added: "We're so lucky in Cardiff to open the doors to world-class talent, and it’s been a riot, getting to work with Kadiff. I’ve loved his work on TV, and stage for a long time, so when we realised he was available and happy to come on board, that was truly a great day in the office!"
Doctor Who returns in just under a month, with a number of additional cast members joining for season 2.
These include Alan Cumming, Rose Ayling-Ellis, Charlie Condou and Kirwan's Slow Horses co-star Christopher Chung, whose character Cassio has "one hell of a meeting" with the Doctor, according to Davies.
Meanwhile, we can also look forward to returning stars including Millie Gibson, Susan Twist and Anita Dobson.
Doctor Who returns to BBC One and iPlayer on Saturday 12th April 2025.
Dive into our Doctor Who story guide: reviews of every episode since 1963, plus cast & crew listings, production trivia, and exclusive material from the Radio Times archive.
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Katelyn Mensah is the Senior Entertainment Writer for Radio Times, covering all major entertainment programmes, reality TV shows and the latest hard-hitting documentaries. She previously worked at The Tab, with a focus on reality TV and showbiz news and has obtained a BA (Hons) in Journalism.
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