John Simm is returning as the Master in Doctor Who
Actor John Simm is returning to play Doctor Who's arch-nemesis, the Master, after a seven-year absence.
He'll battle the Doctor along with a later regeneration of the Master called Missy.
Writer Steven Moffat said fans will have to wait "a little bit longer" to find out more details about the Master.
The tenth series of the show, which starts next week, will also see the Ice Warriors and Mondasian Cybermen return.
"I can confirm that it's true, thanks to the power of time travel I'm back," says John Simm.
"It's always a pleasure to work with this great team of people and I can't wait for you all to see what the Master gets up to in the next series."
The upcoming series will be Peter Capaldi's last as the Doctor.
It will also feature performances from Michelle Gomez as Missy, Pearl Mackie as new companion Bill Potts and Matt Lucas returning as Nardole.
The Modasian Cyberman will appear on the show for the first time in 50 years, whilst the Doctor will have to fend off the new Emojibots.
Steven Moffat, writer and executive producer, says: "Nothing stays secret for long on Doctor Who but you'll have to wait a little bit longer to see exactly what the Master is up to and how he makes his return to face the Doctor.
"It's been a huge pleasure to have fan favourites John Simm and Michelle Gomez face-to-face in the same role.
"It's not often you get to see a solo personality clash."
Doctor Who returns to BBC One on Saturday 15 April at 7.20pm with episode one, The Pilot.