Actor Tom Baker has returned as Doctor Who - re-shooting part of a story which was halted in the 1970s due to an electricians' strike.
Doctor Who: Shada, which has been released as a download, was a run of episodes meant to mark the end of the 17th series, but the studio scenes were never completed.
Baker, 83, has now returned to film part of the 1979 story, which was abandoned because of the strike.
The new scene shows Baker at the Tardis controls in his signature coat and scarf, and combines original live-action footage with new animation.
Baker was the fourth Doctor and his appearance is his first in the role in 36 years.
In the new scene, he voices words from Douglas Adams' original script and wonders aloud: "I expect that sometime in the future - in about 200 years' time - someone will meet me and say is that really the Doctor? He seemed such a nice old man."
Speaking about the cameo, the actor said: "Shada was one of my favourite Doctor Who stories. I have many fond memories of shooting the location scenes in Cambridge, and it was disappointing not to finish the story in the studio."
"When I was doing Doctor Who it was the realisation of all my childhood fantasies," he said, "so I took to it like a duck to water and I still do.
"I loved doing Doctor Who because it was life to me... My real life was really rather drab... I used to dread the end of rehearsal..."
"I never left (Doctor Who) and that's why I can't stay away from it."
Jodie Whittaker will become the first woman to play the Time Lord in Doctor Who in the new series, alongside Bradley Walsh who will play her sidekick.
The BBC series will have a 10-week run in autumn 2018.
(c) Sky News 2017