David Tennant: From time traveller to crime unraveller

He heads a stellar ensemble cast in the new ITV drama Broadchurch, another in a succession of powerful lead roles. But despite his success, David Tennant still worries about being found out

David Tennant, unshaven and sporting a long fluorescent yellow police coat, is staring bleakly into the harbour at West Bay, the seaside satellite of Bridport in Dorset. A body has been dragged from the water and lies on a trolley in front of him. It being a rare sunny day, a crowd has gathered to watch the filming of this scene from the upcoming ITV drama Broadchurch – an eight-part drama exploring the fallout within a close-knit community when an 11-year-old local boy is murdered.

"Clearly it is a murder mystery… a whodunit… but that is a key into a much more complex, richer story," says Tennant when I catch up with him in his trailer. "It's also a story about the family that it's happened to, and the community that's reeling from the death of this child."

Tennant's character, DI Alec Hardy, is an abrasive, formerly high-flying detective, his career under an unspecified cloud, who's sent to this sleepy backwater after the child's murder becomes a media sensation. "I'm shoved out in the sticks to be forgotten about," says Tennant. "And then what should happen but there's a high-profile murder case on my patch."

His arrival upsets local police officer DS Ellie Miller, who believes she should have been in charge of the investigation. Miller is played by Olivia Colman (The Iron Lady, Rev and much else besides), just one component also of an eye-catching ensemble cast that also includes Jodie Whittaker and Andrew Buchan, as the dead boy's parents, Arthur Darvill, in his first job after leaving Doctor Who, and Vicky McClure (This Is England).

"David's a great leader of an ensemble cast," says Broadchurch's creator, Chris Chibnall, who has worked with Tennant on Doctor Who and on the Busby Babes footballing drama United. "He's very, very versatile and he's fearless as well… he's not afraid to try stuff out. When you see the rushes every day you think, 'How has he done that?' Also, on a commercial level, people love him, and that's rare. There are actors you admire and there are actors you love and it's a big difference."

If Tennant secretly shares this high estimation of his worth, he's not letting on. "You don't think particularly tactically as an actor," he says, "you just sort of bumble along. You'll be very lucky if there are two things you get to choose between – mostly as actor you're just going, 'What's my next job? Do I get to eat next month?'"

Actually Tennant's next role is opposite Emily Watson in the Paula Milne drama The Politician's Husband, but surely such insecurity is unwarranted after a varied career that includes an acclaimed Hamlet, Doctor Who and enough voiceover work to make Griff Rhys Jones seem positively parsimonious? "I still feel I'm about to be found out," he says. "So when a great script comes along you sort of bite the hand off really. It always starts with a script – you can spoil a good script but you can't make a bad script good. That initial reaction is very important because once you start investing in it you can't see it objectively again until it's finished."

An eight-hour whodunit about a single murder, with the emphasis on the victim's family – does Broadchurch sound like a certain subtitled Danish drama? "I know the Chris is a big fan of The Killing," says Tennant. Chibnall himself says his influence is in fact Murder One, Steven Bochco's 1996 US TV drama serial in which one criminal trial is followed over 23 episodes. "Around the same time there was Twin Peaks as well," says Chibnall. "Those shows have stuck around in my DNA as I've become a writer."

But did The Killing re-ignite his interest in the possibilities of such a drama? "What The Killing did was that when we got to conversations with commissioners they were more open to it than they might have been five years ago. The serials are in the ascendency again. You think about Mad Men, Breaking Bad, The Sopranos and Homeland and the influence on what the form can do. Television drama is becoming more confident; Broadchurch is like the first 20 minutes of an episode of Law & Order: UK (Chibnall is head writer on that show) spread out over eight hours."

Chibnall lives in this part of west Dorset, just along the Jurassic Coast from Lyme Regis where Karel Reisz filmed The French Lieutenant's Woman in 1981. "When I'm writing and I have a plot point I'm stuck with I go and walk around the Jurassic Coast – I was walking those cliffs and that beach and I'm thinking, 'Gosh it's so cinematic around here and nobody's put it on film for a very long time.' I'd also been working away a lot – I'd been in Cardiff for Doctor Who, and Dublin for Camelot [the 2011 sword and sorcery drama that Chibnall co-created] and I thought it would be good to do something where I live."

The Broadchurch set is as convivial as any I've visited. The cast have never worked together, although their paths have crossed tangentially. Tennant and Arthur Darvill are both ex-Doctor Who regulars, so do they compare notes? "We haven't really," says Darvill. "At the press night for my show [the West End production of Our Boys] both David and Matt [Smith] and Billie Piper came – four of us there from two different generations, and Steven Moffat was there, and Mark Gatiss – it was like a Doctor Who convention really."

Tennant's path crossed obliquely with that of Colman when he provided the cod voiceover for the brilliant BBC2 Olympics comedy Twenty Twelve. "I just saw the end results in a little booth somewhere," says Tennant. "The last ones were so rushed I didn't even get that, I'd just turn up and he [Twenty Twelve creator John Morton] would say, 'Just read these out roughly like you did the last ones… we've got to finish editing today… so quick as you can.'"

'Broadchurch' begins on Monday 4 March on ITV