When we meet, Sir Ian McKellen is about to embark on a dizzying, four-month, global tour to promote The Return o the King, the final part of the Lord of the Rings saga. Just listening to the actor's itinerary exhausts me - it's a real case of "If it's Tuesday, it must be Miami." But McKellen seems not in the least daunted by the prospect of Sydney one day, LA the next - in fact, quite the opposite. He beams with childlike excitement about the very idea of this head-spinning world trip.

"We'll be travelling on Air New Zealand, which has painted the characters on the side of the planes," enthuses McKellen, who plays the heroic 7,000-year-old wizard Gandalf in Peter Jackson's epic trilogy. "This sort of thing doesn't happen very often in anyone's life, so I thought I'd put some time aside to join in."

He is expecting the hype to reach fever pitch at the premiere in Wellington.

"The city closes down and stops being anything other than Middle-earth. When the first film opened there," McKellen recalls, "the authorities changed the name of the city to Middle-earth for one day. All the signposts were altered.

"And for the third year running, all the actors are on the stamps. I'm on the $1.50 stamp and on a coin. The Queen is on one side and Gandalf is on the other! This time round, there is also a huge Lord of the Rings parade that starts in the prime minister's office and continues throughout the city centre, which is totally red-carpeted. How many times have you watched a Royal or a cup-winners' parade go by and wished you were part of it? Well, on this occasion, I am part of the parade." At such events, he laughs, "I get very small children, around five years old, brought to meet me as if I were the Pope."

While he doesn't have quite the global profile of His Holiness, McKellen is not that far off. Thanks to Gandalf - and to a lesser extent, his gloriously evil Magneto in the X-Men franchise - he is now one of the world's best-known actors (as well as one of its bestselling dolls). His impressively comprehensive website, www.mckellen.com - "the autobiography I'm never going to write" -

gets 20 million hits during an average month, but when a major McKellen film opens that number doubles.

But - and this is the good part - fame does not appear to have turned his head. McKellen seems pretty relaxed about the whole celebrity hullabaloo. Indeed, he seems pretty relaxed about everything.

We are drinking coffee on the terrace of his east London riverside house, ensconced between a stone bust of Shakespeare and a bench inscribed with the initials "WHMcK". Taking in the view across an imposing sweep of the River Thames, we are soaking up the last of the late-autumn sunshine.

This has been McKellen's home for the past quarter of a century - he arrived before gentrification, the Docklands Light Railway, Canary Wharf and all that - and it is clearly where he feels most at ease. When a sole swan paddles towards us, the actor breaks off from our conversation, leaps to his feet, greets the bird like an old friend and starts throwing it hunks of bread that he has ready-prepared.

This is the perfect place to wile away three hours in the company of one of the most articulate and thoughtful actors in the business. It is like being treated to a private command performance - a fascinating, complex show for an audience of one.

Casually dressed in a blue T-shirt and white trousers, he is able to express the most sophisticated emotions with the merest twitch of his mobile features. A raised eyebrow here, a frown there, and his demeanour changes in an instant. It is easy to see why he brings a compelling ambiguity to roles such as Richard III or James Whale in Gods and Monsters (for which he won his first Oscar nomination—The Lord of the Rings: The Fellowship of the Ring earned him his second.)

But more than anything, the man has gravitas. This is no flibbertigibbet, fly-by-night, limelight-loving luvvie. When he speaks, you listen, and you are unlikely to hear the phrase, "Darling, last night's opening of an envelope was simply too, too divine" in this performer's sonorous tones. The last thing McKellen wants is to have his equilibrium upset by the turbulent demands of full-on fame. He knows full well that traffic-stopping celebrity "is a very awkward thing. It's actually horrific to have it in your life. It's a great inconvenience. If you're Tom Cruise, then you have to live in a prison."

So how does McKellen avoid being incarcerated in the same jail? Like Baldrick, he has a cunning plan: he palms off any adulation on to his characters. "Gandalf and Magneto are the superstars, not me," he asserts, sipping his coffee from a Richard III mug. "They're icons. Those ‘Gandalf for President' badges are only half a joke. It's on those characters' backs that I ride. They're mighty inventions and whoever had the luck to play them first would have been the beneficiary of people's respect.

"I feel like I'm Gandalf's representative on earth. People keep coming up to me and saying, ‘Hello, Gandalf.' They're not my fans, they're Gandalf's. Which is fine by me because it stops me getting a swollen head."

That's all very well, but isn't McKellen, perhaps the finest theatre actor of his generation, the teeniest bit miffed that he is being upstaged by a 7,000-year-old wizard? "Journalists often ask me, ‘Aren't you sorry that after all the work you've done, you're best known as Gandalf and Magneto?' But that's what I've always wanted - not to be known as myself. I want to draw attention to the characters. JRR Tolkien and Shakespeare are the really great guys. Actors are merely the medium through which a story happens."

All the same, the roles have undeniably boosted his saleability in Hollywood. "Prospective employers can now place me in a way that they couldn't before," McKellen agrees, sparking up a cigarette. "The trouble is, a lot of them think I'm as old as Gandalf so I get offered a lot of old parts, which I'm not interested in. The other day, I was offered God - and you don't get any older than that!"

To try to counteract that, McKellen reveals, he copies Ronald Reagan, of all people. "I once went to the White House for a celebration of Shakespeare's birthday when Reagan was just recovering from being shot. When he was introduced, he ran into the room to emphasise how fit he was. So now I tend to run a lot at premieres!"

A slim, trim, very youthful 64, McKellen certainly seem happy with his lot. He is in control of his fame, rather than the other way round. Most importantly, he feels fully able to be himself; he has learnt to follow Polonius's advice to Hamlet: "to thine own self be true". "If I can be Gandalf or James Whale in front of the camera," the actor muses, "it's because I can be Ian McKellen away from the camera."

But he would be the first to admit that his life has not always been so sorted. He has had to fight various battles in his time - but in the long run he has turned them to his advantage.

The actor's chief regret is that he did not come out as gay long before a famous 1988 live radio exchange with the right-wing editor, Peregrine Worsthorne. It was the time when the Conservative government was introducing the now-notorious Section 28, banning the promotion of gay lifestyles in schools. In mid-debate, McKellen suddenly blurted out: "Let's not talk in the abstract, let's talk about me." In the wake of that dramatic revelation, the actor became a prominent gay-rights activist and, in the very house where we're now sitting, helped set up Stonewall, the campaigning organisation.

"Feeling that it's appropriate to disguise something so central to your nature means that you yourself are homophobic, that you don't like yourself," he sighs, staring into the distance. "Any psychiatrist will tell you that your first responsibility is to like yourself. I'll never quite recover from the fact that for the first 49 years of my life I was fearful of what people would think of me if they knew the truth.

"Self-confidence is what all humans need. When you're up against it, you don't want to start thinking, `If they knew the truth about me, what would they do?' In some societies, they'll stone you to death if they find out you're gay. Even in ours, till I was 27, they would put you in prison. How can I not regret that, at a time when it was illegal for gay men to make love, I didn't stand up and protest? I'm still angry about that."

Emphasising that homophobia remains "rife", McKellen is adamant that there is still much work to be done. "Do those Christians who prevented Canon Jeffrey John from becoming Bishop of Reading understand how we feel? They're saying that just because someone is gay, they shouldn't be allowed to have that job. So people are still allowed to parade their fear and hatred of gay people, and it is thought to be perfectly appropriate."

The actor challenges such prejudice. In a one-man stage show, for example, he tore out of the Bible the page containing that contentious line from Leviticus, Chapter 18, Verse 22: "You shall not lie with a male as with a woman. It is an abomination."

McKellen flashes me a mischievous grin - one of his specialities - as he informs me that the action led one bishop in Scotland to condemn him as "The son of the Devil". The criticism has, if anything, spurred the actor to further acts of defiance; now he rips the offending page out of Gideon's Bibles whenever he is staying in a hotel.

Still, he looks admiringly and perhaps a little enviously at those campaigners who regularly take more direct action. "I see what Peter Tatchell's doing - things like attempting to make a citizen's arrest on Robert Mugabe - and it's brave and necessary work," the actor states in ringing tones. "But I couldn't do that I couldn't be given 10 out of 10 for bravery. I may carry the banner, but I didn't design it. I'm more Alastair Campbell than Tony Blair."

Even so, McKellen has evidently emerged from the experience of coming out much more at peace with himself. And is chuffed to be seen as a role model. "If I had come out at 16, who could I have pointed to?" he wonders. "That vicar in the News of the World? We weren't even called gay in those days. Our word was 'queer' or 'bent' -we were excluded.

"But things are changing for the better now, and I'm a beneficiary of that change. I feel a responsibility to help more change occur. People in public life like me saying, 'I'm gay - so what?' must begin to cleanse the air.

"It would be nice to think that I'd changed some people's lives. I know that people coming out now have said to their parents, 'Ian McKellen is gay, you know' One of the joys of coming out is to realise that you're not alone. I thought I was living with a terrible personal burden, but I discovered that it's actually shared by millions of others. Instantly, you become part of a movement" His eyes are now blazing, fired up by the memory.

"There is nothing more important for the advancement of gay people than being honest with ourselves," he carries on, lighting up another cigarette. "The best thing is to be at ease with ourselves. The more people come out, the more the problem disperses."

For all that, McKellen's commitment to the cause does not extend to running for political office. "I've never fancied going down that route," he reflects. "I've never been good at being a leader - I was the man who famously wouldn't lead the National Theatre. The role of standard-bearer for gay issues was thrust upon me, and I wasn't very easy with it.

"After Section 28, a gay group did ask me to stand for Parliament, and I considered it. I thought it would be fascinating to see how the political process actually worked. But then I said to myself, ‘Suppose I actually got elected—wouldn’t that be dreadful?”

However, the actor has lost none of his political zeal. He has, for instance, been vociferous in his criticism of the government's policy on Iraq. As long ago as February he spoke out that, "War is a sign of failure. A putative war leader is someone who has failed. Failed at diplomacy, failed at compromise, failed to make his point, failed to persuade. Failed."

Sir Ian may have got these pacifist views from his engineer father, who was a conscientious objector during the Second World War. Born in Lancashire, McKellen started acting as a 12-year-old at Bolton, School. After becoming head boy, he went on to Cambridge University. There, in collaboration with such contemporaries as Trevor Nunn, Corin Redgrave, Derek Jacobi, David Frost and Margaret Drabble, he took on more than 20 parts in three years.

On graduating, McKellen eschewed drama school and, in 1961, started working as a professional actor in Coventry. Just eight years later, he was, as the more excitable critics like to put it, "the toast of theatreland", with a landmark performance as Richard II. Harold Hobson described it as being touched by "the ineffable presence of God".

Memorable stints with both the Royal Shakespeare Company and the National Theatre followed, and he delivered performances as Romeo, Dr Faustus, Macbeth, Iago, Richard III and Salieri which were habitually dubbed "definitive".

During this period, McKellen made a string of films without ever really bursting

through as a screen actor. He himself thought his performances were too extravagant for film close-ups - "I was too shouty" - but two pictures in the 1990s changed all that

"Richard III and Gods and Monsters were my breakthrough films," McKellen says. "They showed that I wasn't going to give too big a performance for the camera."

Does he, though, harbour any regrets that film stardom came to him relatively late in his career? There is a pause before McKellen remembers that, "friends say I was always going on about how much I wanted to be in films - maybe I've just forgotten! But the truth is, if I'd been taken up by the movies at the same time as my peers - Albert Finney, Tom Courtenay and Alan Bates - I'd have missed a lot of work in the theatre that I would have regretted missing.

"The RSC and the National Theatre have been a part of my life that I've relished. I might have ended up in a lot of films that I didn't care about as much as I cared about Iago, Macbeth and Richard III. I like what's happened in my career." And who can argue with that?

Success breeds success, and McKellen now has work coming out of his ears. He has two more films already in the can -Asylum and Emile - and is taking his acclaimed stage production of Strindberg's Dance of Death to Sydney in the spring. "There is life after Gandalf," he deadpans.

After that, the actor says, in a phrase that will thrill all theatregoers, "There is Lear looming." As well as fulfilling McKellen's lifelong ambition to play a pantomime dame. "I keep offering and people just smile. Perhaps they don't think I'm serious!"

At an age when many people would be contemplating retirement, the actor seems more eager than ever to embrace new challenges. McKellen's passion has always shone through—both on and off camera.

"Just before my mother died when I was 12," he recollects, "she told my aunt that if I were to become an actor it would be good because I'd really enjoy it. I've held on to that That's why we do it. We hope to entertain, enthuse and, on occasion, educate. Ken Dodd says that he doesn't want to leave the stage without shaking people's perceptions - even if it's only by an eighth of an inch.

"That's got to be doing some sort of good, doesn't it? And that's why, out of 400-odd jobs, I've only ever done three that I'm not proud of." (He loyally refuses to say which they are.) But his enjoyment has taken on an extra dimension since he has become Sir Ian McKellen - Superstar. "People said, 'Your life will change when Lord of the Rings comes out', and they were right," he declares. "There are now very few places in the world where I am not known. To be recognised everywhere is not always what you want, but it is great to have confirmation that what you've done is approved of."

Isn't that all any of us are seeking? Draining the dregs from his Richard III mug, McKellen says, with an air of satisfaction, “Yes, I think I can say that I’m a very contented man. Finally.”