David Tennant and Neil Patrick Harris were spotted filming the Doctor Who 60th Anniversary in the streets of Bristol.
It was announced earlier this week that the How I Met Your Mother actor would be joining forces with Tennant and a host of other returning actors for the special episode.
Catherine Tate will be reprising her role as Donna Noble, and it's thought Bernard Cribbins will also return as Donna's grandfather Wilfred Mott.
Scots Sex Education star Ncuti Gatwa is set to get the keys to the Tardis as the next Doctor, and he will be joined by Heartstopper's Yasmin Finney playing Rose, who many fans believe is Donna's daughter.
During filming in Bristol, Tennant could be seen in his classic trench coat protecting the occupants of a car, while crowds of people were running away.
Fans aren't sure whether Tennant will be playing the 10th Doctor again, or another incantation of the time traveller due to the differences in his costume.
In the on set photos, Neil can be seen wearing a 1920s-inspired suit and top hat as he portrays the mystery villain in the highly anticipated episode.
Sporting The Doctor's famous trainers, Tennant looked visibly shaken during the dramatic scenes as he witnessed the fallout of an explosion.
While one alley was completely littered with standard rubble, another was filled with more mysterious debris, hinting that a sinister alien invasion could be looming.
While much of the street was kept in the present day, a mysterious toy shop had also been erected, and a peek into the window showed an array of wooden toys, board games and a cuddly bear.
Despite it being nine years since he last played the role for the Sci-Fi shows 50th Anniversary, the Bathgate-born actor slipped back into the role like a natural as he filmed the dramatic solo scenes.
Doctor Who 60th Anniversary special will air in 2023.
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