Damon Winter / New York Times News ServicePeter Capaldi is the latest in a long line to take over the leading role in “Doctor Who.” Capaldi brings to the role his own personal take, which he says is more sardonic and elusive.

The passage of time is perhaps not so acute to the centuries-old alien at the heart of the BBC’s “Doctor Who,” the shape-shifting hero known simply as the Doctor, who has had more than 50 years of adventures across dimensions known and otherwise.

But time and its measurement have become especially crucial to Peter Capaldi, who will make his proper, full-length debut as the latest actor to play the Doctor when the new season of “Doctor Who” has its premiere tonight on BBC America.

It has been just over a year since the BBC announced that Capaldi would succeed Matt Smith, who was a 26-year-old relative novice when he was chosen to play the Doctor, and, after three seasons of putting his frantic, whirling-dervish stamp on the character, disclosed his departure in June 2013.

Since then, Capaldi, 56, has spent several months filming “Doctor Who” in Cardiff, Wales, trying to bring to the role his own personal take, which he says is more sardonic and elusive.

Still, as a lifelong “Doctor Who” fan, he could not quite contain his giddiness, all this time later, that he had actually landed the part.

“I just didn’t think that they would be going in this direction,” Capaldi said in a gentle, stately voice with only traces of a Scottish accent, on a visit to New York last week. Asked what he meant, he answered with a laugh: “Well, I guess, older. And more like me.”

Capaldi’s penetrating eyes and expressively lined face will be familiar to viewers of Armando Iannucci’s 2009 film satire “In the Loop,” and the BBC comedy that spawned it, “The Thick of It,” in which he played Malcolm Tucker, a short-tempered political aide who fired off obscene insults as fluidly and creatively as Shakespeare composed sonnets.

But he is still untested as the Doctor, particularly with American audiences who responded strongly to Smith: BBC America said the series grew from an average total viewership of 910,000 in his first season to nearly 1.9 million in his last, a trend the channel would surely like to see continue under his successor.

Though Capaldi is among the more accomplished actors to take on this storied science-fiction franchise, he is hardly a relic. But his age nonetheless represents a departure from the recent history of the series.

It is one more unknown factor for producers and audiences alike to consider as “Doctor Who” begins a crucial transition that elicited passionate criticisms and defenses before Capaldi set foot in front of the cameras.

“When launching a new Doctor, I don’t want to make it sound as though he’s just one of a set of options,” said Steven Moffat, the executive producer and lead writer of “Doctor Who.” “He’s the one and only right now.”

Capaldi is playing the 12th canonical version of the Doctor, though the show cheekily acknowledges its counting system has run off track a bit.

Born and raised in Glasgow, Capaldi grew up admiring character actors like Peter Cushing and John Hurt, and was a follower of “Doctor Who” more or less from the start.

Between the 1960s and 1980s, he watched the series transfer its lead role from elder statesmen like William Hartnell to expressive wits like Tom Baker, and, in its 21st-century revival, heartthrobs like Smith and David Tennant.

As a steadily employed actor, Capaldi said, he’d fallen into a routine of “increasingly bland parts, turning up in episodic television as the slightly untrustworthy doctor or shrink, or the MP with a gay secret.”

“That was fine,” he said, “but quite dull.”

That changed in 2005 when Capaldi met Iannucci, creator of “The Thick of It,” on a day when Capaldi had come from another demeaning BBC audition and was not in a particularly good mood. “I was like, ‘OK, show me what you’ve got,’” Capaldi recalled. “It was lucky I had just the right attitude at that moment.”

Iannucci, the creator and show runner of HBO’s “Veep,” said he recalled Capaldi as initially “very amiable and softly spoken.”

“When the switch came,” Iannucci said, “from this personable charmer to this rather ruthless and cold, frighteningly still person, I thought, ‘My God, that’s quite a trick you can pull off there.’”

Moffat said that the casting of Smith and Tennant on “Doctor Who” had not been a deliberate search for youthful demographics. “When people are trying to be cynical about modern ‘Doctor Who,’ they say, ‘Oh, they always cast these young fellows,’” he said. “We didn’t. It was always a young bloke who turns out to be right for it.”

Moffat said he and his colleagues quickly thought of Capaldi, for reasons he could not entirely quantify.

“He just felt incredibly right,” Moffat said. “He would just take the part in such an unexpected, different direction and overturn everybody’s preconceptions.”