Anthony Hopkins says he's having the best time of his life now. "I don't feel that awful kind of angst - like I was on the wrong planet - that I felt for years. I feel now I belong somewhere. I belong in my own skin."

The man before me is welcoming, well-dressed, toned-down and modest. Though the rounded face, sharp blue eyes and lilting voice belong unmistakably to the famous creature of the screen, Hopkins is reservedly off-duty, more the preserver of mountains than the prolific grandee.

He is here to talk about The Mask Of Zorro, which opens in Britain next week. Hopkins plays the title role of a retired swashbuckler who returns to take on Antonio Banderas as his protègè. There is something curiously un-nostalgic about his performance. Zorro is a man whose past is everything, but Hopkins plays him with barely a visible shadow of his former self.

Hopkins is keen to stress that he has shaken off his youthful shadow. But he may have done more than that: jumbled up his energies and converted his shadow into a positive force. In which case the usual chronology no longer applies.

Before he was a star of the screen, and became the person Richard Attenborough describes as "unquestionably the greatest actor of his generation", he was a young turk of the stage, a stocky, turbulent recruit to the then-recently established National Theatre.

In 1967 he understudied his so-called mentor, Laurence Olivier, in Strindberg's The Dance of Death. Olivier was suddenly taken to hospital with appendicitis, and Hopkins went from sentry to star in a night. Olivier wrote in his memoir that this "new young actor... of exceptional promise...[had] walked away with the part of Edgar like a cat with a mouse between its teeth". Hopkins was bred for the mantle of Sir Laurence, but never felt he fitted in with the "posh actor" crowd or with "over-intellectual directors".

On stage, he was known to be "an energetic and intelligent actor," as one reviewer put it. He had, he knew, "a colossal energy", and described himself as "working like a demon... tearing up the stage"; "like a titan". Even when Hopkins was performing Chekhov, one critic remarked on his "enraged convulsions". "I used to be very temperamental," Hopkins says of that time. "Very difficult. I've always been turbulent, I've never been one of those peaceful characters. But I didn't like that role."

Wedded to a Welsh anger and melancholy was the drink he consumed so savagely. He had in abundance one of the qualities Kenneth Tynan said was required of a great actor - the ability to communicate a sense of danger - and the danger was real. Hopkins was, by his own admission, "not playing with a full deck of cards".

He kept interrupting his theatre work to act in films, and finally, in early 1973, he walked out of a production of Macbeth. Though he has worked at the National since, it is this event that marks the end of that drama - the story of Hopkins the firebrand, Hopkins the drunk, Hopkins who walked.

"I don't want to dictate what you write or anything," Hopkins says softly, and asks me not to make too much of "that subject of booze". He stopped drinking abruptly, on December 29, 1975, when he found himself in Arizona with no idea how he'd arrived. He joined Alcoholics Anonymous, and has attended meetings ever since. "It's just such a long time ago and so boring," he continues. "Someone found out about it one day, and it keeps coming up, like a bad penny." I tell him it's not the alcohol itself I'm interested in, but the instincts and temperament wrapped up in the habit.

He has described himself variously as a "chaotic", "anarchic", "angry", "inconsistent" person, and in his drinking days, in his stage performances, all that was visible on the surface. What we should be interested in now is the alcohol's afterlife - where does the chaos go when the habit is kicked?

"Ah!" he sighs, almost sourly, "the addiction to chaos! The addiction to drama! Never. I never want to go back to that life again. But then I wouldn't have missed it. I wouldn't have missed the crazy years, I wouldn't have missed any of it. It's all part and parcel of growing up, I guess." Now he claims to be "not too fond of chaos", and his anxiety to rein it in seems to be part of an ongoing struggle.

On screen, Hopkins specialises in simmering restraint. Even in characters separated by class - Henry Wilcox in Howard's End and Stevens in The Remains Of The Day - he has perfected a polite holding back of emotion, made up of syncopated pauses and gentlemanly mutterings. Despite his Welsh nationality, for many he has come to epitomise the stiff upper crust of Englishness.

This, of course, only describes the surface. James Ivory, in whose films Hopkins might be seen to have coined that type, is outraged at the "disservice" this suggestion does. "How could that possibly be?" he exclaims. "He has tremendous range. I mean, he's equally happy playing a mad cannibal psychotic and the intensely repressed Stevens the butler."

Hopkins may still be best known for his Oscar-winning performance as Hannibal Lecter in The Silence Of The Lambs. His high, rich voice, flickering tongue, Zen posture and unblinking gaze of impenetrable pleasure have made him a horror hero of historic proportions. As Stevens, he contorted his physical presence into a different shape entirely, almost as if he were wearing the role. He carried himself like a zombie, with a jutting, bovine chin and living-dead arms. He was unbreakably stiff and outlandishly subservient.

But these roles should not be seen as directly opposed to Hopkins's tempestuous performances on the stage. Lecter and Stevens are not lacking in feeling, they are covering it up. The turbulence is there beneath the surface. If on stage Hopkins was all projection, on film he is introjection - but the energy remains the same. Stevens and Lecter are emotion and violence encased in calm, and the tension is what gives the performances their power.

"Tony is permanently in the grip of feelings he cannot control," says David Hare, who worked with Hopkins twice in his later stint at the National. Hare's own play, Pravda, provided Hopkins with one of his favourite characters, the newspaper tycoon Lambert Le Roux, in 1985. And five days after Pravda had ended its 18-month run, Hare directed him in King Lear. This is how he describes Hopkins on days of rehearsal: "He would have got up, played his Steinway for two hours, walked to work from Chelsea, and he would still be the first at rehearsal, having already drunk five cups of coffee, at 9:30 in the morning. He has a fanatical amount of energy he doesn't know what to do with - which is the alcohol problem, so to speak".

So to speak, because by then Hopkins was a decade away from his literal alcohol problem. But intemperance can take many forms, and restlessness is an essential part of his talent, his allegiances, his tireless humour.

He lives in LA now, in a house on a hill, and when he has time to spare he burns off his energy by getting in his car and driving thousands of miles. He says that when he's working he enjoys the drive to the location more than the filming itself. He tells me he likes LA because "there's no past there. The desert burns off your memories."

The people who surround Hopkins day to day will tell you that his memories are one thing that can't be burned off. His capacity for remembering things - detailed things, like times and dates - is phenomenal. He himself says he's "astonished" at his memory, and keeps it supple by learning things by heart - poetry, and Shakespeare. In Steven Spielberg's Amistad he astounded crew and audiences alike with his memorisation of a seven-page courtroom speech, delivering it all in one go. Spielberg was so overawed he couldn't bring himself to call him Tony, and insisted on addressing him as Sir Anthony throughout the shoot.

For an actor, such a memory is a blessing. For a man whose past resists escape, it must at times turn into a handicap. When I ask him about his years at the National he says, "best forgotten, that". Or, "You know, I don't remember much about it". He shuffles his foot in and out of his shoe, turning it over and over on the carpet. He says, almost to himself, "God, it's so long ago", and then he admits. "Well, I do, actually. I remember everything very clearly, but... um... asking these questions is like being on... psychotherapy ...". He takes a deep breath.

Philip Anthony Hopkins was born on New Year's Eve, 1937, in Margam, South Wales. His father and grandfather were bakers, and when the Hopkinses moved to nearby Port Talbot they lived above the shop. Tony was an only child, and ill at ease at school. He was slow academically, and would sit in a corner playing the morose pieces he had learned on the piano. He "used to draw a lot," he says, "and paint". He developed a party trick of drinking indian ink. To distinguish him from the other boys with the same surname, he was called "Mad Hopkins", and even his mother Muriel reportedly said years later, on seeing The Silence Of The Lambs, "I always knew you were strange".

But the boy fell asleep watching the red lights from the cinema opposite flash across his bedroom ceiling. In the school holidays he saw two shows a week at the Regent, and more at the Picture Dome, The Grand, The Majestic. He saw "all kinds of strange, obscure little films which have never seen the light of day since. Jack Palance, Joel Macrea, old Warner brothers movies." He loved Bogart, and Cagney.

Richard Burton's sister lived nearby, and when the young Hopkins went to ask for Burton's autograph, he was inspired by seeing him whizz off in a sports car. Hopkins describes Burton as "a very impressive figure. In a way he was a magical personality because he was the local kid from Tai Bach. I remember thinking, I've got to get out of this place. I've got to get out of this inner sanctum of my own inadequacy and do something with my life."

Hopkins, like Burton, joined the local YMCA players ("for goodness' sake get out of the house and make some friends!" had been his father's exhortation), and it was here that he had his first glimpse of what he could do. He went on to Cardiff College of Drama, then to National service. Hopkins's authorised biographer, Quentin Falk, alleges that Hopkins tried to get out of National service by pretending to be deaf. Hopkins denies this, but even as legend, it shows a young actor before his prime. After two years as a bombardier, he went to RADA, then rep, and in 1965 the National Theatre.

He was praised for his Andrei in The Three Sisters, but even more legendary was his Audrey in Clifford Williams's all-male As You Like It. With long flaxen hair and a silver-tasseled flapper dress, he was "a bucolic Brunnhilde - lumpy, bass-voiced, "grown out of embarrassment", and, according to the Times, "the funniest of all the performances".

Half-way through rehearsals, Hopkins had worried that he wouldn't be able to "make the sexual leap" to play Audrey. That was the time of his first marriage, to the actress Petronella Barker. It was a wrong-footed, short-lived relationship, and a subject Hopkins always wants to "stay off". They had a daughter, Abigail, whom he didn't see for many years. Hopkins and Abigail are now reunited, and, under the name Abigail Harrison, she has had small roles in Shadowlands and The Remains of the Day. Also in 1967 he was given his first break in feature films. He was to play the homosexual Richard Lionheart in The Lion In Winter, alongside Peter O'Toole and Katharine Hepburn.

In this first feature he was full of angst. He could keep still for the camera, but only just - he was burning and seething all over the surface. Ten years later, in Magic, he played a murderous ventriloquist as a nervous seventies boy, an updated Peter Lorre; forlorn and lost. By 1980 he had become the picture of dignity as Frederick Treves, the doctor who rescues The Elephant Man in David Lynch's elegant film. Then came The Bounty, inviting comparisons with Charles Laughton.

He returned to the English stage with Pravda, and in a dazzling feat of renewed energy, played title roles in King Lear and in Antony and Cleopatra in the same season. Hopkins is eloquent about refining his subdued screen skills. "It always feels just right as long as you don't push it," he says. "Sometimes you need to have an explosion, but it has to be measured. I think once you start overacting on film - and I've done my share - it shows badly. Most of the time I think you have to let the audience do the work for you.

"I remember sitting on the pier with Emma Thompson," he says of The Remains Of The Day, "when we were doing the scene at the seaside when I had gone to meet her. It was one of those yellow autumnal afternoons, a yellow sky with a black cloud underneath, and I thought, I don't have to do anything."

Richard Attenborough, one of the first film directors Hopkins ever worked with, describes his effortless transition from stage to screen thus: "The theatre was his nursery. And he therefore became obsessed with the sound of words. The magical thing he understands is that the cinema is a totally, totally different medium. And that silence is nine times out of 10 infinitely more effective than words".

Hopkins has made 22 films in the past decade. Of these, he is most accomplished in Nixon, most hammy in Bram Stoker's Dracula, and most true to his Welsh past in August, which he directed in 1995, and for which he wrote the music. soon after our first meeting, he will be on his way to Rome to begin shooting on Titus Andronicus, Julie taymor's film of Shakespeare's violent, rarely performed tragedy.

"I've always wanted to be in movies," Hopkins reflects. "I never felt at ease in a theatre company. I think it smacks too much of school. But that's something inside me. I just reacted as a bad schoolboy brat. In film, you have no illusions when you go on set. For me working on film now is just about being relaxed, knowing the script so well that you don't have to think about it. Then you rehearse in front of the crew, and there's a wonderful... smell about it, a wonderful feeling of... in its own way, its own creativity. A charge in the air - a charge sounds too intense, but some sense of, I don't know, atmosphere."

"SILENZIO!" The cameraman shouts, and the Italians do their best to keep quiet. It's a warm, fairly calm day on the set of Titus Andronicus. Behind richly dressed senators and guards in Roman helmets rises the impossibly grand facade of a white marble building commissioned by Mussolini. Off-camera, all the ancient Romans are wearing sunglasses. People are chatting and gossiping, hanging around, passing through. It's a friendly set, and an awesome pleasure to see Hopkins in his element.

Julie Taymor is up on the platform showing people where she wants them to stand. The cameras are ready. Off to one side, Hopkins is having a deep-red leather cape fitted over his metal-coated shoulders. His white hair is cropped to nearly the same length as his speckled stubble. He walks over to where the action is about to begin. "Rome," he announces, "I have been thy soldier 40 years, and led my country's strength successfully."

While they re-load the cameras, he roams about, making cheerful quips and issuing bear hugs. He greets me warmly and introduces me to his colleagues. He behaves less like star than a host - how is my hotel, have I had lunch, how long am I here? Then the crew are ready to go again.

Hopkins's wife Jenni is over for the weekend. They met in 1969, when she was working as a production secretary and was sent to pick him up at the airport. He was in a sorry state then, but they've lived through better times. Now Jenni sorts out his work arrangements in London, and generally plays the part of the grounded other half ("My wife is so sane she's mad," Hopkins says). Though they are still married, they have lived apart since 1996, she in London, he in California.

At the start of that year, there was a brief blast of tabloid attention when Hopkins announced in an Alcoholics Anonymous meeting that he was having an affair with an actress named Joyce Ingalls. It was, he was quickly quoted as saying, "a moment of madness", and the reunited couple established their transatlantic living-pattern for the future.

"My wife and I have a great relationship," he tells me. "An easy-going relationship. And we've come to terms with it. She lets me do my thing. This is my life, I live in hotels, and when I have time off now I get in my car and drive thousands of miles. It's a solitary life, but I love it."

Jenni has a sprightly, refined grace. She has a small, smooth, freckly face, twinkling blue eyes and reddish hair. She greets me on her way to lunch, every bit as warm as him. Over lunch, I find myself chatting to a very jovial man. "You can ask me," he says brightly, "I know everything about him." "OK," I say, and a look of abject horror passes over his face. "Nah, not really. You'll have to ask him yourself." This is Terry, Hopkins's stand-in. Does that mean he's his double? "Nah, if he needs to do a stunt or something, they'll get a stunt double."

He's not a body double and he's not an understudy. Terry's job is to be there so shots can be set up and lights can be arranged without Hopkins being present. "We've got the same build, the same blue eyes, and... well, I don't want to put myself down too much, but I'm not as clever as him. We've got the same sense of humour."

Hopkins, evidently, is inspiringly silly when relaxing. "Anyone who knows him well will tell you the same thing. He's got incredible talent, and he's amazing, he can switch it on and off." Terry has had cameos in a few films: as the gamekeeper in August, the registrar in Shadowlands, and the DJ in Gary Oldman's Nil By Mouth. Hopkins calls Terry "the Hitchcock of the Hopkins clan" because of his split-second appearances.

Hopkins once said that his way of relaxing was to watch Carry On films, and as soon as this pair are together the vaudeville begins. Egged on by Terry, Hopkins impersonates Burt Lancaster, then Gary Cooper, Jack Lemmon and Tony Curtis. He runs through the classics, replaying segments line by line. I ask him if he could impersonate himself. "Oh, yes," he says without a pause. "There's a man on the set who does a very good impersonation of me. Gary Oldman does a wonderful one. He goes like this" - Hopkins stands up - "he says 'Come on, let's get on with it!'" He is growling and prowling around like an animal in a boxing ring. "'Come on, lights going! Come on, We're not puppets!'" He snarls, snapping his fingers, then breaks into laughter. "Like I'm always looking for a fight. But I've always had that energy."

When the day is over Hopkins sits down with me again. He is more blatantly irreverent than before about the crowd at the National Theatre ("I detested all of them. Ken Tynan and all those ghastly people, sitting round smoking their cigarettes between their middle fingers"), and more nostalgic about Port Talbot.

As he describes his father and grandfather a self-portrait emerges, full of impatient energy and demotic defiance. Asked what it means for him to be Welsh, he replies that he is not tied to anything. He can't speak Welsh, and often inverts the stereotype by insisting he can't play rugby or sing. He has no opinions on the question of devolution. He mentions only meekly the fact that he "put some money on a mountain", and his donation of a million pounds to Snowdonia, far from being some territorial gesture, sounds like something Mr and Mrs H decided over tea: "I said to my wife, 'how about putting up some of the money?' She said, 'Yeah - you think so?' And I said, 'well, we're quite well off, and I'd like to do that'."

But in talking about his father, his attachment to Wales and to the rebel spirit he inherited becomes very clear. "My father was a man of colossal energy. So was his father. Violent energy. I think that's what killed my father, he was so wound up. His eyes used to change colour. "My grandfather was dynamic, self-educated, brought up in terrible poverty. His father drank away everything. So my grandfather had to make some money and ended up in a German bakery in Piccadilly. And he became very active in the trade union movement. They were firebrand socialists and my grandfather used to demonstrate in Trafalgar Square. But he mellowed over the years. He was a self-educated man, a vegetarian - a crank. An extraordinary man. I used to shadow-box with him," Hopkins laughs, "and he paralysed my arm. "I don't know, I feel that their memories are embedded in me. I wonder sometimes if we inherit the memories of our parents... Fanciful stuff, but I've got some photographic books of Port Talbot, taken earlier this century. And some aerial photographs of my birthplace taken by the Luftwaffe about 1940. And you can see the whole of Port Talbot laid out, and trace the streets.

"And I look at those aerial shots, and I think somewhere there, my grandfather was baking and my father was somewhere on the bread van, a young man. And I go back, I conjure images of what it would be like to start my life all over again." "My mother, she's 85, she says, 'God you're just like your father'. Well, I think, that's not a bad person to be." Hopkins smiles.

Something else comes to him. "There's one story that sums up my father. I was doing a production of A Woman Killed With Kindness at the National, with Joan Plowright and Derek Jacobi - posh actors -and Laurence Olivier came to see us on the first night. Oh, that's right, we were sitting in the pub before, my father had just come up from Wales with my mother. He said, 'What's this like - Shakespeare, is this?' "I said, 'No, it's not Shakespeare, it's a Jacobean play.' He said, 'Ah yeh, any shooting in it?' My mother said, 'Oh Dick'. He said, 'Well, it's all very well 'angin around here doing Shakespeare and all these classical things, you want to make money.'

"So anyway, they came to see the play and afterwards they were in the dressing room, and Laurence Olivier came in. And I said, 'Oh, Sir Laurence this is my father, this is my mother'. He said 'What did you think of the play,' and my father said, 'Ooh, I'd give it a fortnight'. And he said, 'how old are you?' Olivier said, 'I was born in 1907'. He said, 'Same age as me. Both going down the bloody hill now, aren't we?'

"Olivier smiled and he said the next day: 'What a charming man your father is'. My mother said 'Dick, how could you say that?' He said, 'Well he breathes oxygen, just like me'. I always remember that - he breathes oxygen, just like me."

The next day on the set, Jessica Lange is there, in full gold-armoured regalia. Alan Cumming is wearing a laurel wreath and giving a piggyback to Jonathan Rhys Meyers. I bump into Hopkins straight away. "Have you had lunch?" he asks, and invites me into his trailer. "I don't eat much," he says, offering me his meal, unwrapping little tin parcels of rice and chicken.

The trailer he's in belongs to some famous Italian actress, he doesn't know who. It's nicely decked out, with architectural engravings on the walls and blue pastel curtains. He sits at the little table, shuffling some papers about. He says gently, "You were asking Terry about my scripts?" I had been curious to know whether Hopkins still drew pictures in his scripts. "Oh yeh," Terry had said, "wonderful." And Arthur, Hopkins's dresser, who has been with him on a number of films, had described with awe the actor's method for learning his lines.

"He reads them once and draws an X. He reads them twice and makes a star out of the X. He reads them again and draws a circle around the star. And all over his scripts there are hundreds of these tiny circles and stars. He reads each line over 300 times." Hopkins passes me a clump of pages. "Here they are," he says. "I just doodle in them, you see. On the backs of pages, on the loose pages. They help me to remember the lines."

The drawings are beautiful, somewhere between stream-of-consciousness sketches and classical paintings, all in multi-coloured felt tip. There are minimalist landscapes, Picasso-esque faces with droplets of tears, an eyelashed Neptune surging from the sea, a hilltop tomb in purple and orange. Some of them look like pastels by Odilon Redon.

In fountain pen, Hopkins has written little literary notes to himself: "Cantos", "Metamorphosis - Ovid." Lines of dialogue are highlighted in green and yellow and blue - orange and red for the violent scenes. There are the stars Arthur mentioned and numbers in circles for the amount of times a line has been read - 120, 250, 300.

Here is the private world of the man who is an addict of detail and loves broad swathes of colour; a dispenser of rigid control with a propensity for chaos. His is an intricate, rigorous method, and it looks quite brilliantly like madness.