IAN MCKELLEN conjures up a new role: LORD of the box office.

Go to New York’s Times Square. Nod in deference to the two-story Lord of the Rings billboard looming above. Then turn onto 44th Street, slip down the circuitous back stairs of the Broadhurst Theatre, and you will find Ian McKellen in his dressing room. Fresh from a performance of August Strindberg’s Dance of Death, the 62-year-old actor lights Dunhill reds off a squat candle and graciously answers the tap-taps at his door: A string of admirers want to pay respects. But the kudos aren’t all aimed at his tricky work on stage. Of late, McKellen’s fan base has broadened beyond theater aficionados to include comics buffs (thanks to his villainous turn as Magneto in 2000’s X-Men) and J.R.R. Tolkien enthusiasts (see that Lord of the Rings billboard). Considering his silvery hair, throaty British cadence, and crisp tweed trousers, who’d have guessed this is a guy anchoring two massive sci-fi franchises?

”We were doing a photo shoot in Times Square, and two black guys, young guys, saw me and said, ‘Magneto! Hey, man!’ They were high-fiving and all that. The Brit didn’t know quite what to do,” says McKellen. ”In [theater], you can begin to think you’re only working for a small group of people within society: middle-class, probably middle-aged, probably university educated. Like me. Film is a much more popular medium, so now I feel I’m a bit more of a citizen of the world.”

A much-favored one: The first installment of the Tolkien trilogy, The Fellowship of the Ring, is dominating about 10,000 screens to the tune of $435 million worldwide — and McKellen is winning raves for his role as a certain volatile gray wizard. ”He was simply the first and only person that we wanted to be Gandalf,” says Ring director Peter Jackson. ”He’s the kind of actor who disappears — you see him in that beard and the oily hair, and there’s no Ian McKellen anymore.”

McKellen himself wasn’t entirely sure he wanted to take up the magic maker’s staff. ”I didn’t know Gandalf from hobbits,” he admits. ”Then I heard year’s work, three films, big project — and thought, That’s just, perhaps, what I want to do.”

In the end, McKellen signed on, despite having never seen any of Jackson’s infamous gore flicks. ”Thank God I hadn’t, because if I had…it’s not to my taste, all that stuff.”

The 15-month, effects-laden shoot throughout New Zealand was novel for McKellen, who’s spent much of his four decades as an actor amassing awards for treading the boards — in fact, the last time he worked at the Broadhurst, in 1980, he won a Tony as Salieri in Amadeus. Despite screen work since the late ’60s (as a gay activist in And the Band Played On and a doomsaying preacher in Cold Comfort Farm, among others), it was, suitably, his 1995 adaptation of Shakespeare’s Richard III — in which he played the king as a Hitlerian despot — that marched McKellen into Hollywood. ”If it hadn’t been for Kenneth Branagh’s cheek in making his own Henry V when we all know Olivier’s version did it all…” he says. ”It made me think, as much as I admired Olivier’s Richard III, maybe there’s room for another version.”