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One Saturday teatime in 1966, the popular childrens' television show "Doctor Who" did something rather clever. The star of the show was replaced by a new actor, paving the way for the show to last for 50 years (and counting).

Unfortunately "The Power of the Daleks", the first adventure in which Patrick Troughton replaced original leading man William Hartnell, was lost to history -- until now.

That landmark story was shown only once because the master tapes were erased, a common money-saving practice in the days before repeats or videos. But the BBC has re-created "Power of the Daleks" in animated form using shooting scripts, still photos and original audio recordings. The restored -- or should we say reanimated -- adventure is coming soon to stores, to Periscope, and even to movie theatres.

Anneke Wills, who played the Doctor's companion Polly in "Power of the Daleks" and many other missing episodes, could barely contain her excitement at a preview screening of the animated restoration.

"To see Polly and Ben [played by the late Michael Craze] animated is a treat, because so little of our work survived," she said. "We live!"

When filming, Wills and Craze were aware that the change from original leading man William Hartnell was a risk.

"Michael and I were thinking, 'Crumbs, I hope we'll be in work next week'. We didn't know if the public would accept it. But [Patrick] was so adorable they did accept it."

Director Charles Norton explained that Patrick Troughton's expressive face was a gift to the animators. The characters are animated very simply -- this is no Pixar production -- but somehow that adds to the vintage feel. TV in those days was rather stagey, and it takes a few moments to get used to the slightly awkward pacing. But the story is a tense and engrossing affair, and when the Daleks threaten, you can see why fans hid behind their sofas.

"I love it", said Wills of the restoration's charmingly wobbly animation. "It's very 'Who'."

The six episode serial will be available to British fans at the online BBC Store on Saturday 5 November at 5:50 p.m., exactly 50 years after it was first shown at that exact time on 5 November 1966.

International fans can share the excitement of gathering to watch the show at a set time, just like viewers the first time around, by watching the first three minutes of the serial via Periscope. Visit twitter.com/bbcstore at 5:50 p.m. GMT (10:50 a.m. Pacific time or 1:50 p.m. Eastern time) to see the clip, which includes the groundbreaking regeneration scene.

The animated adventure will be screened on BBC America on 19 November. Fans can also enjoy it on the big screen at selected movie theatres on Monday 14 November -- click here to find your nearest screening.

The DVD goes on sale on 21 November. Bonus materials include a documentary, commentaries and a look at the fragments of footage that survived when the serial was lost.

The producers of the restored "Power of the Daleks" haven't ruled out animating more of the 97 episodes of early "Doctor Who" that are still missing. In the meantime, the series returns to television on Christmas Day with Peter Capaldi once again playing the Doctor.

Fifty years after her own stint in the Tardis, Anneke Wills offers this advice to new companion Pearl Mackie: "Enjoy it -- it's the best job in the world. And in 50 years you could still be talking about it!"