'I'm pretty much the absolute apex of a charming, disarming, likable kind of personage': Tom Hanks, perfectly chosen as Hollywood's first Aids hero, talks to Simon Garfield

On Saturday nights the President of the United States likes to hang loose and screen movies at the White House. A few weeks ago he showed Philadelphia, the Aids drama. Tom Hanks, the star of the movie - the star who dies at the end of the movie - turned up to meet the Pres and First Lady and share the gourmet popcorn. Bill and Hillary had a few doubts about some of the courtroom details.

'They're real legal weenies,' Hanks says. 'But I think they liked it, and at the end they said they hoped it would change attitudes and opinions.' Then they asked Hanks about the make-up.

Philadelphia is a moving Hollywood experience, a plaintive tale of homophobia, discrimination and justice. One of the opinions it changes is the one we hold of Tom Hanks. Hanks has been as anonymous as you can be while still being a major movie star. There is no story on Hanks, no terrible past, no coke binges. The worst it gets is a mid-Eighties divorce at which he lost custody of two kids. He's a pretty good actor, nice-looking if you like them puppy-style, but otherwise as predictable as beige.

He says: 'I'm 37, I've made 17 movies, and my joke is that four of them are pretty good. Well, four of them are OK, just about worth watching.' These include Big, A League of Their Own and Sleepless In Seattle. And now Philadelphia, in which he finally graduates, shaves his head, and is being talked of as the biggest shoo-in for a Best Actor Oscar since Charlton Heston jumped on that chariot (Hanks has been nominated before, for Big, the year Dustin Hoffman won for Rain Man).

He's making the most of it. On the pretext that Silence equals Death, he arrived in London a fortnight ago for a spot of PR. Impressed by his new depth, his incisiveness, I was expecting a bit of a fighter, a bit of the film's gay Andy Beckett character, who gets dismissed from his law firm when a senior partner notices a lesion on his forehead. More fool me: I got a hetero softy, an appeaser.

'You're a bit of an empty vessel,' I said.

'That's actually a great compliment,' he said. 'It's good to be as blank a canvas as possible, because then the audience fills it in.'

For Hollywood's first dollars 30m (pounds 21m) Aids movie, Hanks is a good choice. The real issue of the film, he believes, is why so many people fear and loathe gays. 'It makes great sense to have someone who is not particularly fear-inducing or loathsome in the role, and I'm not. Very few people fear me. There might be some people out there who loathe me, but I'm pretty much the absolute apex of a charming, disarming, likeable kind of personage.'

He's modest then, and apolitical, too: 'I have no political (he searches for the right word) bent.' Wrong word. But surely this will change now, and he will take up Aids as a great cause and rattle tins? 'No. I'm very sceptical about anyone using their Hollywood celebrity in order to sway anything. I remember being 13 and seeing Sonny Bono at the Republican national convention and thinking 'What is that guy doing there?' I don't think it does any good. There are a lot of organisations that keep coming at you all the time, wanting you to do this for them or that for them, but if you do ' Uh-oh, the slippery slope. Too far in to rescue himself now: 'If I was to go out and try and truly believe in something and crusade for it, then I wouldn't be an actor.'

But Hanks does do some stuff - he turns up for an American Foundation for Aids Research benefit alongside Barbra Streisand, and he 'tithes' anonymously. It's just that he doesn't believe in red ribbons, the emblem of Aids awareness. 'It just becomes a trifle after a while, a nothing. It becomes an issue of who didn't wear it. Anything that happens on television now, they have a red ribbon. So do you have to wear it? Is it still an option? Is it just a publicity thing? I don't know any more. It's like Kafka after a while] My God, I mean, how much do you have to do? I didn't wear one at the Golden Globes, and someone called up my publicist. I mean, for crying out loud] It ends up being comical, but tragically comical.'

Hanks did a lot of research for his role. He talked to doctors and to people with Aids. He even talked to his hairdresser. 'I asked the man who did my hair what the bathhouses were like. He said, 'Oh, the baths, it was this amazing place where you could walk in and have anonymous sex '.' Hanks adopts this bug-eyed, born-yesterday face. 'The techniques are fascinating stuff] I can hardly believe that it exists, and want to read every detail. And I did, in fact, and some of it was shocking, and I thought, 'They must be embellishing' I mean rimming (oral-anal contact) that stuff's amazing.'

Before Hollywood became serious about him in the mid-Eighties, Hanks used to live in Times Square, the crotch of the world's sex industry. He went to plenty of porn shows, but never experienced the gay scene. He says he was a little envious of it, and that there probably wasn't a young heterosexual man in the world who wouldn't want to live the same kind of hedonistic life for a while, 'especially when there's no information as to how dangerous that can be. I just thought it was wild. I wondered how often in the history of the world does this come along? Is this Berlin in the Thirties? Is this Rome in the first century?'

Hanks grew up mainly in San Francisco. His mother left when he was young, his father remarried several times, but he says he remained sheltered and nave until his late teens. He was shocked when he learnt that his high school drama teacher and several of his college classmates were gay.

These days he knows lots of gay men, and many with HIV. A good school friend died of Aids, as did a cousin. He says he does feel a little uneasy about cashing in on the disease. He is sympathetic towards the criticisms levelled at Philadelphia, of which there have been many. He recites them, mantra-style, almost as penance: 'The gay community says that the film is not a real accurate reflection of their lives, that my character is not your average gay man. They say he's in the closet. They say that his family is too supportive of him. We're damned if we do, and damned if we don't. These are all valid criticisms, but they don't come from the people whose lives are really like that. They said there wasn't any close love scene, but if there had been, they would have said, 'Are we supposed to accept that Tom Hanks and Antonio Banderas (his screen partner) are believable as they lather each other in the shower?' There's no sleep to be lost by reading bad reviews. I've read great reviews that I thought really got the movie, and I've read horrible reviews that I thought also really got the movie.'

Hanks has now entered what he calls his 'six-week window of specialness', that twilight world between nomination and Oscar night when 'the tension and the nerves can just screw your head right off'.

Has he thought about what he will say if he wins? 'The important thing is to get on and get off without doing or saying something that will embarrass you for the rest of your life.'

But will he say something about Aids?

'Of course, but I don't know what yet.'

Maybe he should ask his hairdresser.

Philadelphia' opens in London on Friday.

(Photograph omitted)