For his current role, as Ariel in the RSC's The Tempest at Stratford, he has had his hair cropped short and dyed blond, which suits him; he has lost weight, and he is deeply tanned. Far from being ugly, he is mesmerising to watch. He has the same stocky, bull-necked quality as Anthony Hopkins, all power concentrated in the chest and shoulders, eyes lit as though from behind by sheer mental energy.
We are talking in Adrian Noble's deserted office at the Royal Shakespeare Theatre in Stratford. It is a perfect summer day. The place is thick with tourists. Tonight, the main draw will be Russell Beale's crop-haired, spitting Ariel - an inspired piece of casting by the 26-year-old director, Sam Mendes. His elusive Ariel is no Tinkerbell, but a malevolent sprite with kohl-rimmed eyes in a silk suit.
For all his presence, he is tantalisingly evasive: I had the sense that he was acting an interview. He spoke warmly of his family, teachers, friends and fellow professionals. All were 'remarkable', 'extraordinary' (his two favourite words), or just very, very nice.
It came as a surprise when he said he had a hot temper. This 32-year-old actor, seemingly launched in a pyrotechnical arc towards a theatrical knighthood, of whom Noble said: 'I would put millions of pounds, if I had them, on his becoming a star' an angry young man? Much later in the conversation he divulged what was possibly, he thought, the reason for this anger, and after that many things slid into place.
First, his background: comfortable, cosmopolitan, cultured. His father was an army doctor and the family travelled the world. Simon, the oldest of four sons and a daughter, was born in Penang in January 1961. 'We're still a close and happy family: they're my best friends, probably because of my mother. She's an extraordinary woman. I don't know what she did or quite why we all love each other so much.
'My middle brothers and I all went to the same prep and boarding school, but first I went to St Paul's Cathedral Choir School at the age of seven. Except at the very beginning, I was very happy there.
'I used to go home every holiday, and it was still the world of amahs (Malayan nannies) and servants. It was also the era when a major, as Dad was, had a big white house with french windows and verandas, so flying out there was all rather glamorous.'
Yet it was not a pampered life. 'The thing about choir school is that it trains you musically like no other system. I was locked into a room every morning for an hour or so to play the piano, and it inculcated an extraordinary professionalism. Also, for three or four hours a day you are forced to perform - to sing - with no excuses and no mistakes allowed. The place was run by a priest and his wife, and he was an absolute martinet. You didn't move without his permission. That legacy of discipline is still there.'
Did singing in daily services from the age of seven to 21, and being steeped in the Bible and the Book of Common Prayer, leave a spiritual legacy?
'Not exactly a religious thing, as far as I'm aware: except that the history of the Church generally has become an obsessive interest of mine. If I could hold medieval history between my hands . . .' He cups his hands, and in that brief, vivid gesture cradles Abelard, Erasmus, and all the Popes between. It is a lightning moment; the only time throughout our interview he makes a theatrical gesture. 'Medieval holy Roman politics, also the 20th-century church: I find all that fascinating. Give me 10 years and I shall probably convert to something. I wanted to go under instruction - here in Stratford, actually - but I'm a coward. One's waiting for the blaze of light but, as Augustine says, not yet. I do have a hankering after people who are spiritual. It's a whopper, all that.'
The young Simon went on to public school at Clifton College, Bristol. 'I had, as a lot of actors do, an extraordinary English teacher with whom I still keep in contact and admire enormously, and he can be a rigorous critic of what I do. I still start by analysing the text of a play: that's his influence. After O-levels, when I thought I was going to be a doctor, he said to my parents: 'Don't be surprised if he ends up an actor.' '
At Cambridge he came across another charismatic teacher. 'I arrived full of the best and worst of all that discipline - a sort of unsentimental rigour, but also an insufferable arrogance. I remember being told my first essay was a disgrace. Gradually, over the next two years, I found that there was a value in an emotional response. Eric Griffiths was an enthusiast for Victorian poetry, a very great and glamorous teacher, and I asked to be taught by him. He took great delight in teaching me Tennyson and was also the person who gave me the push into acting.'
Although Russell Beale insists that he is not particularly intelligent, merely well-educated, he got a First in English at Cambridge and contemplated the academic life. 'I went to Eric Griffiths' rooms and said: 'I suppose I should enquire about a PhD?' He said: 'Oh don't be so stupid.' '
His thesis, inspired partly by Tennyson's In Memoriam, would have been about the death of children. 'In Memoriam revealed to me that you could get excited emotionally, and that sort of loosened me up. I got sort of into grief.' His lava flow of language has slowed down; he is hesitant. Then he reveals: 'It was about mourning because I had a sister who died. I was 11. She was about four. That was a big thing in our family. I have a melancholic taste in poetry still.'
A year ago, Russell Beale played an electrifying Richard III. He used a huge hump and built-up shoes to conjure up a squat figure of concentrated malice. Afterwards it was found he had seriously damaged his back, and he had to undergo an operation. 'I've never cried consciously as an adult, but coming out of the anaesthetic I sobbed and sobbed. Yet even then, there was a little part of me that was using that emotion. I thought, so that's how it feels to wrench it up from your guts. When my parents are in the audience I worry. What goes through the heads of people who love you, and see you go through that pain on stage? They must think: 'Where did he find all that, and who's responsible?' '
After this disclosure he slips back into his actor self. Is he morbid? 'Death, thank God, has not loomed large in my life, though it will do, I know. I haven't lost close friends yet.' He refers, I assume, to the fact that, being homosexual and in the theatre, it is inevitable that Aids will claim people he knows. 'I am gay, you know that,' he confirms. He is not willing to discuss it further. Fair enough.
Russell Beale was at Cambridge at the turn of the Eighties with a group of highly talented theatrical people including Kenneth Branagh, Emma Thompson, Stephen Fry, Hugh Laurie, Tilda Swinton and - most significantly for him - the directors Stephen Unwin and Jenny Killick. 'My friends didn't feel like a charmed circle, though I was aware there were some pretty special people doing their stuff. But Stephen was a big influence. He gave me my first big part at Cambridge and professionally. It was extraordinary how magisterial an influence he had on a lot of people, considering how young he was. We did believe that what we were doing was worth while.'
Despite this, when he came down from Cambridge he went to the Guildhall to study music. 'I don't know why I took so long to decide to be an actor. I'd never lived in London before except at choir school, and they didn't allow us out except in groups of 30, under strict supervision. I had no money and I found London frightening. And I soon realised that I was completely unsuited to being a soloist. Mine was never going to be anything but a pretty voice, and it wasn't the career I wanted.
'Then I organised an Edinburgh Festival production with Jenny, which was a great success. I was at my most fiery then. I used to get very angry, but it was frustration, because I hadn't got the technical facility for the acting I was doing.'
He had talked earlier about always feeling himself to be a second-rate singer. Did he feel himself to be a first-rate actor? 'There are moments when I think I'm probably Second Eleven: I mean that quite seriously. Acting . . .' He frowns and pauses and stares out of the window. 'I don't know whether I'll ever make people gasp, and this makes me quite melancholy sometimes. It's very important to get your self-regard about right. It's very easy to get overblown in acting - and the reverse.'
'Having started by doing so much comedy, when I switched to more serious works there was still the nagging doubt that I would walk on stage and it would be funny. I'd come on as the avenging angel and they'd laugh. And they haven't. I have to believe that I'm interesting, just standing there.'
Other than his passion for medieval history, what else engages Russell Beale outside the theatre? Surprisingly, politics. 'I vote Labour. I think one of the most depressing nights I've ever had was that last election. I'd got the champagne in the fridge and, then, well, how quickly it all went wrong. It saddened me that they weren't given a chance.
'There are lots of things for which I'd march. It's been in the back of my head for some time to join Amnesty International. It's a funny thing about being an actor: there are occasions when you think, am I doing any good? There is a spiritual side of you that does think, well, part of my life ought to be helpful to people in trouble.'
I ask what he gets out of acting. 'Not the showing-off, not the applause, though that's extremely nice. I just love exploring pain and . . . what it feels like. It's partly a way of dealing with the intensity of emotion.'
It is 21 years since his little sister died. It would be glib to assume that Simon Russell Beale has just confessed that acting exorcises that early bereavement, and crass to ask outright.
He goes on: 'Acting is physical exercise. I suppose it is my sport and that physical exorcism has been the name of the game for the last seven years.'
The interview over, he took me on to the main stage. Slightly raked, its backdrop is a curve of deepest blue, into which an invisible door is set. 'That's my door,' he said proprietorially. 'The designer said: 'At least I've given you a good exit.' I vanish through it, Pfffut]' ' Vanish? In an odd sort of way, the man behind the hump and the imp had hardly even appeared.