A Scottish Actor to Star in ‘Doctor Who’

When a science-fiction hero has lived for centuries, journeyed to the farthest reaches of the universe and been reincarnated multiple times, how much change can he undergo in 50 years?

Apparently, only so much.

On Sunday, the BBC said that the Scottish actor Peter Capaldi will be the latest actor to star on “Doctor Who,” its long running adventure series, and will play the 12th official incarnation of a time-traveling, shape-shifting character known simply as the Doctor.

The announcement was made during a live program seen on BBC America (which shows “Doctor Who” in the United States) and closely watched by faithful viewers around the world. But it was a bit of a disappointment to those fans who hoped that, for the first time since the Doctor was introduced in 1963, the character might be played by someone other than a white man.

“It’s so wonderful not to keep this secret any longer,” Mr. Capaldi, 55, said on the BBC special. “But it has been absolutely fantastic, in its own way.”

In recent weeks, audience speculation (as well as betting odds given by British bookmakers) about the new identity of the Doctor had coalesced around Mr. Capaldi, who played a government bureaucrat with a blisteringly obscene vocabulary in the political satires “In the Loop” and “The Thick of It.”

But other “Doctor Who” fans had been encouraging its producers to consider a black leading man like Idris Elba, a star of the BBC crime series “Luther” and the HBO drama “The Wire,” or David Harewood, of the Showtime thriller “Homeland”; or an actress like the Academy Award-winner Helen Mirren, or Olivia Colman, who has starred in the British murder mystery “Broadchurch.”

Mr. Capaldi will inherit the role of the Doctor (and his time-traveling TARDIS vehicle) from Matt Smith, who has portrayed the character since 2010, and who announced in June that he planned to leave “Doctor Who” at the end of the year.

Mr. Smith was 26 when he was announced for the role. The choice was mildly controversial at the time, at least among those viewers who worried he was too young to play the character.