On Sunday night, when Scottish-born actor Peter Capaldi was revealed to be taking over the magic screwdriver to portray Doctor Who in the cultishly popular BBC sci-fi series of the same name, many American fans greeted the news with some confusion.

Doctor who?

Replacing Matt Smith, the on-call Doctor since 2009, Capaldi arrives as the oldest actor to portray the Time Lord since William Hartnell first embodied Doctor Who on British TV in 1963.

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Moviegoing audiences may have most recently caught Capaldi, 55, portraying a medical professional with a different relationship to the Hippocratic oath -- an actual doctor for the WHO  -- a World Health Organization medic in the Brad Pitt zombie thriller “World War Z.” And American audiences will have further chance to acquaint themselves with the Scottsman’s on-screen mien through his high profile supporting roles in such films as the Wikileaks biopic “The Fifth Estate” and the Angelina Jolie fairy tale fantasy “Maleficent.”

But Capaldi -- who won a 1995 Academy Award for live action short for “Franz Kafka’s It’s a Wonderful Life,” which he directed -– casts a long shadow in British film. He burst on the scene with a breakthrough performance in the 1983 comedy-drama “Local Hero.” Appearing alongside “Animal House” alum Peter Riegert and Burt Lancaster, Capaldi whimsically portrays an awkward, young oil company exec who learns the Texan conglomerate for which he works plans to buy a small Scottish village and turn the bucolic backwater into a refinery.

Showing a range that has crossed all genre boundaries, the actor can also be seen in 1988’s “The Lair of the White Worm,” joining forces with Hugh Grant to battle -– you guessed it -- a giant blood-sucking worm and its attendant platoon of evil vampire queens; in the comedy “Bean”; the drama “Smilla’s Sense of Snow”; the period sex romp “Dangerous Liaisons”; and alongside James Gandolfini in the 2009 political comedy “In the Loop.” In that film, Capaldi reprised the role that made him a household name in the UK –- the venomous communications officer he played in the mordant British TV satire “The Thick of It,” for which the actor won a 2005 BAFTA.

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But if Capaldi seems familiar to denizens of “Who”-ville, it’s because the actor -– a self-described life-long “Doctor Who” fan -- has already popped up in relation to the series twice. In “Doctor Who” Season 4, he portrays historical Roman citizen Caecilius, and he guest starred in five episodes of the “Doctor Who” spin-off series “Torchwood” in 2009.

The “Doctor Who” selection process has been shrouded in secrecy for months, known internally within the BBC as “project Houdini,” with only 10 people reportedly allowed inside the circle of trust regarding the actor’s hiring.

“It is so wonderful not to keep this secret anymore,” Capaldi said Sunday on British television. “For a while, I couldn’t even tell my daughter. 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. I can’t wait to get started.”

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chris.lee@latimes.com

Twitter: @__chrislee