“Doctor Who” fans will finally be able to enjoy a newly completed classic episode of the sci-fi show after producers and former series star Tom Baker filled in the blanks of an unfinished 1979 installment titled “Shada.”

The episode had remained incomplete for decades after an engineering strike disrupted filming. BBC Worldwide, the commercial arm of the pubcaster, has now stepped in and completed the episode with an animated segment and a new scene starring Baker, the fourth Doctor.

The new scenes were shot at BBC Television Center in London on the set of the original Tardis. It shows the Doctor, clad in his famously long coat and stripy scarf, emerging from under the time-traveling machine’s console.

Baker briefly reprised his role as the Doctor in a segment of a charity special, but this is the first time he will have appeared in new footage in a regular episode of the classic series since his 1974-81 run as the time lord.

“When I was doing ‘Doctor Who’ it was the realization of all my childhood fantasies…so I took to it like a duck to water and I still do,” Baker said. “‘Doctor Who’ was more important than life to me – I used to dread the end of rehearsal….That’s why I can’t stay away from it.”

“Hitchhiker’s Guide to the Galaxy” author Douglas Adams wrote “Shada,” in which the Doctor and his companion, Romana, battle an alien called Skagra in the picturesque English university town of Cambridge. The Shada of the title is a high-security prison planet. The episode has been adapted as a radio play and is the subject of much chatter among “Doctor Who” fans.

“’Shada’ was one of my favorite ‘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 studio. I’m so glad that BBC Worldwide [has] found a way to bring fans a complete visual version,” Baker said.

Charles Norton, who was behind the animation of lost “Doctor Who” episode “The Power of the Daleks,” produced the restored “Shada.” A new soundtrack including music and sound effects has been composed by Mark Ayers, using the original equipment of the 1970s. The new episode will not go out on “Doctor Who” broadcaster BBC One but has been packaged as a digital download and DVD special by BBC Worldwide.