Tom Baker, who played the role of The Fourth Doctor on Doctor Who for seven years, has returned to play the character after decades.

Baker, 83, last appeared as the Time Lord in 1981, after which, the character regenerated and Peter Davison took over as the next Doctor. As the longest-serving Doctor in the BBC sci-fi series, he will reprise his role by donning his signature hat, long coat, and stripy scarf to film new scenes for an unfinished episode that had to be abandoned mid-way.

The Lost Episode

Famous sci-fi author Douglas Adams, whose credits include the famous novel series, Hitchhiker's Guide to the Galaxy, penned the episode titled "Shada." However, filming for the episode, which was supposed to be the end of the 17th series of Doctor Who, came to a halt. The episode had to be shelved due to an industrial strike at the BBC.

Now, BBC Worldwide has put all the filmed scenes together and with the help of original scripts, replaced the missing scenes by using animated versions of the characters voiced by the original actors. The story will be released decades on as a feature-length film and Baker makes a cameo appearance as an old man.

The producers have made use 1970s camera equipment and shot the scenes on the original TARDIS set and K9 robot dog model in order to make it look exactly like the original footage.

"Shada" will be set in Cambridge where the Doctor and his assistant, Romana (Lalla Ward), team up with a retired Time Lord, Professor Chronotis. Together, they will defeat the alien, Skagra, who has an evil plan of trying to steal intergalactic secrets to the prison planet of Shada.

The lost episode will be available to buy on digital download and will be released on DVD and Blu-ray on Dec. 4.

Baker on Playing The Time Lord Role Again

Talking about reprising his role as the Time Lord, the actor said that he stopped playing the character more than three-and-a-half decades ago but the character never left him.

"That's why I can't stay away from it, it was a lovely time of my life," he said. "I loved doing Doctor Who, it was life to me. I used to dread the end of rehearsal because then real life would impinge on me."

Baker has played the role of the Doctor in audio plays and made his last on-screen appearance as the Time Lord in 1993 "Children in Need" special. He also made an appearance in the 2013 50th anniversary special, The Day of the Doctor, but as the curator.

Check out the teaser trailer for "Shada" below: