Not-so-simple Simon

Beale says he is not friends enough with Mendes to ask about his love life. The first he knew of the Winslet romance was when the Press phoned him for a comment. He is close enough, however, to lobby gently for film parts. Apart from anything else, a role in a movie by Mendes, who made American Beauty, would transform his finances, which have sometimes been precarious. Sixteen years working as a lead for the RSC and National makes you rich in prestige but, at £650 a week, buys you a small flat in Pimlico, which is where Simon lives alone, and sometimes lonesomely.

"I keep on dropping hints and then he announces that the next one is going to be about gangsters in Chicago. Oh Sam, come on! What about one about fat middle-aged white men in England?"

Fat is a thespian issue for Beale. He had nervously yearned to do Hamlet ever since his Konstantin in The Seagull in 1991 - in fact he talked to me about it at around the time - yet when the moment finally came, he felt the only thing he had to bring to the role was his body. "I just thought there hadn't been many people my shape doing Hamlet and that could be a disaster or it could be an advantage." As one paper put it, "Tubby or not tubby, fat is the question." It is quickly apparent that Simon's opinion of himself is not nearly high enough, and you would be unlikely to go far wrong in attributing this to looks which, in less enlightened times, would have ruled out many of the leading-man roles he has already played on stage. Off stage, he still seems to think himself somehow disqualified.

When I say it is a pity he has done so little on film and television - nothing memorable, really, except for his wonderfully inept Ken Widmerpool in Channel 4's A Dance to the Music of Time - he admits: "To be perfectly honest, I don't particularly like watching myself on screen."

Any compliments you offer a face such as Beale's will seem patronising, so I will refrain. The point is that he is intolerant of his looks and, even more so, of his body. The recurrence of his back problems, reignited as he was cooking Christmas dinner, is another symptom of its recalcitrance, and today he buries it amid the scruffiest T-shirt and undone shirt imaginable. His self-criticism may be all the more severe because he is gay, although he says he does not feel a victim of male gay culture's lookism. Anyway, he is 41. "Perhaps when you're older looks become less important. He says hopefully."

His dissatisfaction with his appearance has led to a more generalised marking down of his talent. He says he is fascinated by second-rate characters such as Iago and Widmerpool. "Most of us, I suppose," he says, "are second-rate."

But surely the days of his self-loathing should be over by now. "No, it's all still there. I don't know why, but it just is."

But it's 10 years since he last talked about this to me, I say. "Was that meant to help?" he just about jokes. No, I say, but it has been a decade of real achievement and acclaim. That his insecurities are so remarkably intact is at least handy for playing Humble Boy's hero, Felix, a quantum physicist whose name (Latin for happy) mocks his disgruntlement. Although there are as many differences as similarities between Hamlet and Felix - not least, says Beale, that Felix has actually had sex - both plays are about a son's intense relationship with his mother after his father's death. Both plays deny their scholarly heroes the conventional consolations of religious faith.

Simon was a choirboy at St Paul's from the age of seven and, as a boarder, attended a church service almost every day of his childhood aside from holidays. From Clifton College in Bristol he went up to Gonville and Caius, Cambridge, on a choral scholarship. The words of the hymns have stuck and in 1993 he predicted to an interviewer that within 10 years he would have " converted to something".

"I still haven't taken the leap," he confesses. "I was doing West End Sings, which was a thing at Christmas where we all sang carols and I was asked to do a reading - 'There's a time to mourn and a time to dance' - and the priest of Covent Garden was there and I said, 'Oh, I really would be interested in instruction.' He looked at me really - " he leaves the word blank. "But he gave me his number, so I suppose..."

What stops him believing? "The central leap of faith that God sent His son to earth. I just can't do it. Yet."

He has suffered two great bereavements in his life. His four-year-old sister Lucy, who had been born without one of the chambers in her heart and spent much of her life in an oxygen tent, died when he was 11. His mother, Julia, did, he believes, a remarkable job in keeping the remaining family of boys close during this period, the more so since his father, Peter, was a military doctor and the family spent most of Simon's childhood abroad. He was not unhappy at boarding school, but the smell of starched linen on a sleeper he took to Edinburgh recently transported him instantly back to a forgotten memory of the misery and loneliness of his first night in the dorm.

In the spring of 2000 Julia Beale, who was a GP herself, died of pancreatic cancer. In her last months he was not working during the day and was able to visit her in Swindon and return to London in the evening.

"She was proud I was about to do Hamlet. I had to lie at one point about when it was opening. She said, 'Will that be in June?' and I knew it wasn't opening until August or something and so I said yes. I didn't think she would make June anyway but that was horrible because I thought, 'Supposing she lasts until June and I have to say it's not until August.'"

In the event she died in May, a note he had written for Mother's Day unopened beside her. He now wishes he had read it to her. "There are all these myths about dying, aren't there, and one is that hearing is the last thing to go. I thought, gosh, the last thing she will have heard are my footsteps going click, click, click."

When Hamlet opened, actually in July, he had the cast's permission to keep a photograph of her in the wings and he dedicated his performance to her. The reviews, which he had vowed not to read, were sensational.

"What Hamlet allows you to do is - and it just sounds so crass - but it allows you just to be yourself. You're interesting as a human being. It's such a reactive part. Everything happens to him. He doesn't initiate very well. And you just have to have faith that you, Andrew, me, Simon, standing on stage is an interesting thing.

"With the big, high-definition parts like Richard III and Iago, probably less with Iago (I think I was a bit too high definition), it isn't really possible to do that. Too much pizzazz. But with Hamlet I was just standing on stage at the end and going, phew, sorry, but that's me: spiky, arrogant, facetious, all the things that Hamlet was." Did he emerge more comfortable in himself, though? "I wouldn't say that, really. I mean, I've still got the same old worries and insecurities. I just learnt something about acting, really."

Hamlet has helped him a little, for instance, to face the camera's close-ups in The Gathering, a film he has just completed with Stephen Dillane, a supernatural thriller in which he is a priest. But in life?

"You're right in the sense that what Hamlet did show is that you can be - 'loved' is the wrong word because that's too sentimental - but you can be of interest, warts and all. Somehow. But no, I think the self-doubts and self-loathing are there. I wish they would go away."

Has he finally got partnered up? "No. I don't think it is going to happen."

I say he is such a lovely guy that it will. It happened, for instance, to Stephen Fry, that awkward-looking ex-singleton. "You're very sweet, but we'll see. In a way, that particular pressure has come off because I'm now actually quite prepared to be single. At 40 you think if that's God's plan for you, then that's God's plan, and you do the Pollyanna bit and say you are lucky in so many ways, blah, blah, blah."

My own feeling is that pretty soon, Beale, whose 41st birthday was on Saturday, will break through into his life's uplands and he'll be lonely no more. At the moment he is still marching across the forest floor, and has not yet quite passed Elsinore. It is compelling progress to watch, less easy, I imagine, to live.

Humble Boy previews at the Gielgud Theatre, W1, from 24 January.