The Bathgate-born actor is about to open in a new production of Look Back in Anger at Edinburgh’s Royal Lyceum Theatre, having spent the last few years forging a successful career on both the small and big screens.
Smaller roles in acclaimed pieces such as Jude, starring Christopher Eccleston and Kate Winslet, have led to bigger parts in similarly well-received productions such as Stephen Fry’s movie Bright Young Things - not bad going for an actor who landed his first part in television by a "bizarre fluke" after pictures sent in to Scottish Television landed him a part in a children’s drama.
And the 33-year-old Scot’s role in the seminal social realism play in the Capital comes hard on the heels of filming a movie which is guaranteed to bust box office records - the latest instalment of the big screen version of Harry Potter.
Tennant will be seen by millions as Barty Crouch Jr, the son of a Ministry of Magic official who has ended up as dark wizard baddie in Harry Potter And The Goblet Of Fire, something the actor is looking forward to tremendously.
"It’s just great," he gushes. "It just such a huge, big thing isn’t it? . . . an enormous rumbling franchise, and it’s nice just to visit that world for a bit."
Tennant, who was brought up in Paisley, has worked with some big names during his career but, given that Harry Potter reads like a veritable who’s who of British acting, was there anyone he was in awe of?
"Not really," he says. "I knew Michael Gambon, Maggie Smith and Alan Rickman anyway, having met them or been in things with them down the years.
"It was actually just really good fun, particularly getting to listen to Michael telling ribald tales for a few days."
The Harry Potter part came about after Tennant starred in a play last year at the National Theatre. Nothing unusual in that you might think - expect when you consider that in Martin McDonagh’s The Pillowman, Tennant played the role of a horror writer being interrogated by the police following the violent deaths of several children.
"Mike Newell, the Harry Potter director, came to see the play and then he offered me the part. It was pretty straightforward - though they did have to send a tape to America, seeing as they didn’t know who the hell I was."
Tennant has also played a young Casanova to Peter O’Toole’s older character in a yet-to-be-seen biopic for BBC Three. All of which is a fair way from his first role - in an episode of a children’s series called Dramarama when he was 16.
But his career proper began after he left the Royal Scottish Academy of Music and Drama in Glasgow, in 1991 - although it had taken Tennant’s parents some persuading that acting wasn’t a completely insane profession to enter.
"I think, quite rightly, my parents thought it was a pretty stupid profession to go into in terms of job security and things like that.
"Like any parents, I think they were just a little bit nervous that maybe I’d end up living in a cardboard box in Sauchiehall Street."
So did he have a plan B ready, just in case the acting career failed to take off in the way thought?
"No, rather recklessly I didn’t have any back-up," he admits. "Because I was so single-mined, I never entertained the idea that acting wouldn’t work out."
He stayed in Scotland for a short while after leaving drama school before heading to London. From Saturday, though, he is back in his home country, treading the boards in a new production of one of the most famous and influential plays of the second half of the 20th century. When John Osborne’s Look Back in Anger was published in 1957, having been first performed the previous year, the play caused uproar and controversy among writers and critics.
Rocking the establishment with its hard-hitting themes and gritty, social-realist style, the play changed the face of British theatre forever.
Look Back in Anger, it has been said, brought the drama of working class life to the stage for the first time. It might be almost 50 years since it first appeared, but according to Tennant the play has lost none of its ability to disturb.
"I think it probably still does have the power to shock," he says. "It certainly still has the power to move."
Probably so, but does the leading man think audiences will see beyond the play’s anti-establishment reputation?
"I hope so, because I don’t think that’s principally what it’s about," he says. "The historical significance has slightly made people believe that anti-establishment is what the play is about. But really, it’s not about the politics of 1956. The play is about these three people living in one room together and tearing each other apart."
Among them is the play’s chief protagonist, Jimmy Porter, played by Tennant. He is a passionate, articulate and educated man, trapped in a dead-end job, sharing a bed-sit with his wife and best pal.
But more than anything, Porter feels anger at the economic and intellectual poverty in which he is trapped.
So was it hard to go from straight-forward Harry Potter baddie to a complex angry young man?
"You just try to get yourself into a relaxed, concentrated state of mind," he says. "That way you can let the part take you where it needs to."
So how much of an impact on his future does he feel that appearing in the most sure-fire box-office hit of the year will have? "I wouldn’t actually think it will make much difference to me," he says, playing down his "minor part" in the grander scheme of things.
"Just about everyone outside of the kids are relatively small parts and I’m just one of the British luvvies lined up to do their bit.
"I don’t imagine it will change my life particularly, but I’m just very proud to be a part of it."
And confessing that he doesn’t have any work lined up after Harry Potter, Tennant jokes that his involvement with the boy wizard could spell an end to his career. "This will probably be the last you hear of me now," he jokes.
Don’t bet on it.
Look Back in Anger, Royal Lyceum Theatre, Grindlay Street, Saturday to February 12, 0131-248 4848