Shada was meant to be a celebratory episode to conclude the 17th series of Doctor Who, and was written by Douglas Adams, most famous for penning book The Hitchhiker's Guide to the Galaxy.
The actor, 83, has returned to film part of the 1979 story, which was abandoned because of a strike by electricians.
Doctor Who star Tom Baker has reprised his role as the Time Lord - to re-shoot part of a story which was halted in the 1970s due to strike action.
Worldwide have dug out the original scripts written by Douglas Adams to complete the episode using animation, voiced by the original actors.
Baker stepped down from the role in 1981 after seven years and was followed by Peter Davison.
How Duterte Sabotaged the Philippines Peace Process
Duterte issued Proclamation 360 on Thursday, terminating peace negotiations with the NDFP. Sison also lashed at Duterte, calling him "the No. 1 terrorist in the Philippines".
He also appears in the flesh, in new, live-action footage of the Doctor as an old man.
Daniel Hill, who was at the beginning of his acting career when he was cast in Shada, said he was thrilled to see it on screen at last. I loved doing Doctor Who because it was life to me.
But rather than just being a celebration of, well, eating, Doctor Who Day holds a lot more meaning.
And now fans celebrate November 23 every year as Doctor Who day - the day the sci-fi series came hurtling into our lives back in 1963.
Baker said the Doctor character "probably never left me". I used to dread the end of rehearsal because then real life would impinge on me. Shada - an episode that began filming in 1979 with Tom Baker as the legendary Time Lord - is finally finished and available to download (a DVD will be released in the United Kingdom on December 4th, and in the USA on January 9th).