Peter Capaldi is the new "Doctor Who"

Peter Capaldi is going from spin doctor to "Doctor Who."

The BBC announced Sunday that the Scottish actor, best known as venom-spitting political fixer Malcolm Tucker in the sitcom "The Thick of It" and its film spin-off, "In the Loop," is the new star of "Doctor Who," the famed science fiction series soon to celebrate its 50th anniversary.

The identity of the new Doctor had been the subject of frantic speculation, and the revelation was made with fanfare befitting one of Britain's best-known shows - during a live suppertime television broadcast.

Capaldi is the 12th actor to play the Doctor, a galaxy-hopping Time Lord who travels in the Tardis, a time machine shaped like an old-fashioned British police telephone booth. At age 55, he's also the oldest since the first Doctor, William Hartnell.

Capaldi, a fan of the show since childhood, said that "being asked to play the Doctor is an amazing privilege."

"Like the Doctor himself I find myself in a state of utter terror and delight," he said.

Capaldi has a long list of movie, television and stage credits, from the 1983 film "Local Hero," to zombie thriller "World War Z," to the BBC's recent newsroom drama "The Hour." He is currently playing Cardinal Richelieu in BBC drama "The Musketeers." He's also an Oscar winner -- he directed "Franz Kafka's It's a Wonderful Life," which won the Academy Award for best short film in 1995.

"Doctor Who" was first broadcast in 1963 and is now one of the BBC's most popular programs, both in Britain and abroad. Its longevity is due partly to the flexibility of the premise. The Doctor can regenerate into new bodies and can travel to any point in space or time.

"Doctor Who" ran from 1963 to 1989, and was revived to acclaim in 2005. Since then, the Doctor has been played by Christopher Eccleston, David Tennant and Matt Smith, who took the part in 2010.

The role will be a dramatic change from Capaldi's turn as Tucker, a political manipulator known for his ceaseless and creative use of expletives. "Doctor Who" is a firmly child-friendly program.

"I think Malcolm has been banished from the mirror by this Doctor Who, who certainly would not put up with any of Malcolm's language or attitude," Capaldi said on the BBC show Sunday.

He also talked about how it was difficult to keep the secret under wraps: "For a while I couldn't tell my daughter, who would be looking on the Internet and discovering that people were saying so-and-so should be Doctor Who. She was getting rather upset that they never mentioned me."

Smith will leave after a November episode to mark the show's 50th anniversary and a Christmas special that will see him regenerate into Capaldi. Capaldi's first full episode will air next year.