A number of characters from the previous Doctor Who series will return for an episode to mark the BBC’s centenary.
The Masters, Daleks, and Cybermen will appear later this year, as will two of Doctor’s former partners, who will reprise their roles for the first time since leaving the show.
Janet Fielding, who played Tegan Jovanka between 1981 and 1984 will return, as will Sophie Aldred, who appeared as Ace alongside Doctor Sylvester McCoy from 1987 to 1989.
This will also be Jodie Whittaker’s final appearance as The Doctor, after her departure was announced last year.
He made his first appearance as the 13th Doctor in 2017. His successor has yet to be announced, but his name is expected to be confirmed in the next few weeks.
Sacha Dhawan will reprise his role as The Master for the episode, having played the doctor’s arch nemesis in series 12 in 2020.
The comeback was revealed in the trailer broadcast following the special event on Easter Sunday.
Fielding said: “In some ways it was a very different experience to what I felt when I finished recording in 1983, but in many ways it was very similar. It’s great to be a working member of the Doctor Who family again.”
Aldred said: “It is quite a challenge to keep such a big secret, even from my family, and I am very happy and excited to be asked to return.
“I hope everyone enjoys it as much as I love being part of the Tardis team again.”
Along with Whittaker, host Chris Chibnall will also depart. He will be replaced by Russell T Davies, who was behind the show’s 2005 comeback, after 16 years away from the TV screen.
Chibnall said: “Jodie’s final feature-length story contains plenty of treats and surprises for audiences and fans alike, not least the return of two of the most beloved friends in the show’s history.
“They will help the Doctor fight on three fronts, against his deadliest foes: Masters, Daleks, and Cybermen, in one big story.
“For the BBC’s centenary, we will celebrate the past, present and future of Doctor Who in this thrilling, epic and emotional release for Doctor 13.”