Peter Capaldi will be joined by the First Doctor in the 'Doctor Who' Christmas special.
The 59-year-old actor is set to bow out of the series following the upcoming festive episode and David Bradley's First Doctor will help him say goodbye.
In a cliff-hanger ending to the series 10 finale, Capaldi's Doctor was fatally shot by a Mondasian Cyberman and begin to regenerate. Stepping out of the TARDIS into an arctic landscape, he fought off the glowing regeneration energy and fell to his knees, vowing that this time he would not live on and change into a new Doctor.
However, this was declared "ridiculous" by an approaching figure, who mocked the Doctor as he stepped forward through the snow to reveal himself as the very first incarnation of the TimeLord.
He said: "The Doctor? Oh, I don't think so. No, dear me, no. You may be a doctor, but I am the Doctor. The original, you might say."
The story is set to continue in the Christmas special, where Capaldi's replacement will be introduced.
This will also be the first multi-Doctor episode since 2013.
David previously played actor William Hartnell playing the First Doctor in the drama 'An Adventure in Space and Time' as part of the show's 50th anniversary celebrations in 2013.
Hartnell played the first incarnation of the Doctor from 1963 to 1966 but passed away in 1975.
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