Star Wars actor Ian McDiarmid returns home to Scotland after more than 35 years

"I remember three-a-days, they were fun," he says, a flush of nostalgia in his voice. "I did three-a-days at the Citz as an ugly sister. That was a great company, Tim Curry as Buttons, Cheryl Campbell as Cinderella, Jonathan Kent (with whom McDiarmid would later direct the Almeida Theatre for 13 years) as a snow pixie. Do put that in, it's important he remembers that."

And McDiarmid twinkles mischievously. At 64, he's a small, wiry man with that distinctive profile, the receding forehead, the nose. (Casting him as Galactic Emperor Palpatine in Star Wars, George Lucas is reported to have said: "Great nose".)

For all that he gets described as prickly and private, he's talking 19 to the dozen about his current project, his own adaptation of Andrew O'Hagan's novel Be Near Me, which he is rehearsing with the National Theatre of Scotland. He talks as he moves, fast, as if he stayed in one place for too long someone might pin him down.

Being back at the Citz, though, is a kind of homecoming. McDiarmid was raised in Dundee, but after 35 years of distinguishing himself on the stage in London and New York (most recently with a Tony Award for Faith Healer on Broadway in 2006), he has come back to his native land. He has bought a house and now spends at least half his time here.

"If you'd said to me five years ago, 'In five years' time you'll have somewhere in Scotland and you'll be doing a play up there with something called the NTS', I would have said: 'Well, I can tell you, you're absolutely wrong!'" he laughs heartily. "So what do you know?

"And I wanted to get back. I found slightly, in spite of myself, a kind of pull. Maybe you do that as you get older. The more you think you've escaped the past the more it sort of intrudes. And I'm not unhappy about it."

So he still feels Scottish? "Yes, I do. In the 1980s I did a play at the National Theatre in London about European exiles in America, and the director made us all sit down and say, round the table, all our family influences. And I got rather depressed because I'm Scots through and through. I felt disadvantaged because my blood wasn't as colourful as everybody else in the room. But now I think it's just fine."

One of the things that drew him to O'Hagan's novel is its theme of identity. McDiarmid will play David Anderton, an Oxford-educated Catholic priest who takes a parish in a depressed post-industrial town in West Ayrshire. Lonely and alienated, he is drawn to a group of local teenagers until a homosexual indiscretion has him branded a paedophile.

It's a controversial subject – I get the sense McDiarmid is quite excited at the possibility of stirring up a variety of opinions – and it doesn't exactly show the country at its best. Reviews of the book – which was longlisted for the Booker Prize – describes Dalgarnock as a "hellhole" populated by sectarian Neanderthals. One critic said that if it existed, the best thing to do would be to blow it up.

McDiarmid insists that the view of Scotland is as complex and ambiguous as anything else in the novel. "It's also very funny, and I'm sure in the hands of those skilled actors (the company includes Jimmy Chisholm, Kathryn Howden and Taggart's Blythe Duff among others) it will be very funny. Anyway, we know what we're like, don't we, we Scots?" he adds, and chuckles cryptically.

Everyone in Dalgarnock is struggling for an identity. Even Father David doesn't really know who he is. Those around him flounder in a world of closed factories and thwarted dreams.

"It's an interesting thing identity," says McDiarmid, thoughtfully. "Some of us are fortunate enough to have one in as far as what we wanted to be when we were younger we've been able to be, I'm certainly a case in point. But that happens, I think, in relatively few cases."

He knew he wanted to be actor ever since, as a small child, he was taken backstage at a variety theatre in Dundee. He was enthralled and terrified by the lights, the greasepaint, the strange pretend magic of the theatre. Though he did a degree in psychology to please his father, he then headed straight for the RSAMD.

After a couple of years at the Citz, he went south, working at a string of major theatres. He branched out into directing, first at the Manchester Royal Exchange, then at the Almeida, which he and Kent transformed, attracting the likes of Kevin Spacey and Cate Blanchett to a little-known Fringe theatre. It was often assumed that he and Kent were a couple, though they were not. McDiarmid will say nothing about his private life other than that he lives alone.

As he grew in maturity, he clocked up increasingly ambitious roles: Edward II, Henry IV, Prospero, The Jew of Malta. He was most recently on television in Channel 4's City of Vice with Iain Glen, and has played Denis Thatcher in the forthcoming BBC drama, Margaret.

And now David Anderton. I confess to McDiarmid that I'm not really sure what to make of him. He's lonely but aloof, clever but also at times remarkably stupid. He's a snob who takes refuge in fine wines, quotations from Proust and memories of a long-lost gay love affair, rather than attending to his duties as a priest.

McDiarmid agrees. "It's precisely that ambiguous quality that makes him dramatically interesting to me. The characters that I'm most drawn to are the ones with the most contradictions. He's packed with those. Sometimes I want to hit him, there are characters in the play want to hit him and you think, 'Yeah, quite right too'. Other times you think, 'Poor soul'."

By coincidence, earlier last year McDiarmid played a Cambridge-educated clergyman in a relationship with a younger man in Robert Holman's Jonah and Otto. One writer described it as "the quintessential McDiarmid role, introverted and unfathomably sad, yet with great reserves of compassion". That's Anderton, too, in a nutshell, but McDiarmid is curt. "Actually I haven't had many of those roles. People are usually saying, 'Why do you always play villains?' I think that writer was comparing Otto with (Ibsen's] John Gabriel Borkman (another of his roles last year], who most people would describe not as unfathomably sad, but as a self-centred bastard."

What irks him most, however, is that there would be any notion of a "typical" McDiarmid role. "I would always want to fight that. Just as I hope there's not a typical McDiarmid either. I always want to resist description because I think I'm always changing. I'm not anything that's fixed, I'm always in transition."

So he is mellow about the fact that, despite his successes in some of the most demanding roles the stage can offer, he is destined to go down in history as the arch villain in Star Wars. Appearing in five of the six films, with an expanded role in the three "prequels", is what gives him the financial security to pick and choose his projects.

"The Emperor's been good to me. He's been terrible to everybody else, but good to me. That's his one redeeming quality! Those films were huge fun for me, and they did give me a bit of money. And I like George Lucas very much, I admire him. I got to know him rather well over the years."

And McDiarmid is off, a man moving fast lest he stand still and find himself typecast. "Someone said to me, do you know what you're doing after May (when the Be Near Me tour ends)? And the answer is no. It's always been like that. I like the fact that I can continue to be in transition. We're lucky in the theatre because it's on and then it's off, I love that, and then you're on to something else."

Be Near Me opens at the Palace Theatre, Kilmarnock, January 14-17, and then tours in England and Scotland until May.

Background

IAN McDIARMID loved Andrew O'Hagan's novel Be Near Me as soon as he read it. Telling almost no-one, he penned his adaptation in a matter of weeks last winter. After it got the thumbs-up from friends, he sought a meeting with the man he dreamed might direct it, John Tiffany from the National Theatre of Scotland, who directed Black Watch and The Bacchae.

Within a matter of weeks, he was invited back to Glasgow to meet NTS chief executive Vicky Featherstone. "Before they'd even sat down and got their coats off, Vicky said: 'We want to do it.' I was overwhelmed." Swiftly, everything fell into place: an opening in Ayrshire, a run in London and a tour of Scotland and England.

But the really terrifying moment came after a read-through when Tiffany suggested that the play needed an extra scene. "I said: 'Who's going to write it?' And he said: 'Well, you're the bloody writer'. I said: 'But it's not in the book' and he said: 'Well? You'll have to invent it, won't you?'

"So I got on the train in a panicked state, and I had an idea which led me to the scene. I had to get some paper from the guy on the tea trolley, because I thought I'd forget it by the morning. By the time I got back I'd half written the scene. And Tiffany said: 'Don't give me all that rubbish about not being a writer!'."