By Ariel leve.

Tom Cruise has never had a drink problem. He has never made an embarrassing sex tape or been photographed storming off the set or fighting in public with a girlfriend. He has never become paunchy or jowly or bloated. It's unlikely he'll ever be spotted wandering aimlessly around Malibu in pyjamas. He doesn't moan about the paparazzi or break down on the Oprah Winfrey show crying about his oppressive childhood. He doesn't bare his soul or his wounds. At least not publicly.

He's not tormented and he doesn't wallow - about anything. Ever. Ask anyone, friends or fans, what they think of Tom Cruise and "nice guy" will be in their response - decent, generous, professional too. In an industry where people feast on the carcasses of one another's failures with glee, he remains respected and well liked.

Even a limousine driver, after breaking the sacred covenant and dishing the dirt on some of the celebrities he's driven, describes him as "Polite. A good tipper." There's nothing "dirty" about Tom Cruise. At least nothing we know of. And therein lies his gift. The biggest movie star in the world - a man who has made 27 films, grossed more than $2 billion at the box office in an 18-year career - retains a unique super-power mightier even than his incandescent grin. He is universally liked while being universally unknown.

It is early evening on the Paramount studio lot, and before the golf cart has reached the sound stage where our interview will take place I am made aware of the sanctity of "time with Tom". I have been granted 45 minutes of his undivided attention, and in Tom's world, where minutes are worth millions, it resonates. It is a big deal. These are 45 minutes during which he will not be jumping off a building, or climbing up a rock, or ironing out a plot point, or being in transit from one very important place to another. He is unfailingly organised. Every second of his life is utilised and seized for maximum value. His life is a tightly programmed machine. But is he?

This much I am told: the interview will end at precisely 7.15pm. It is now 6.25pm, and I have been collected from the hospitality suite and am led down a long, carpeted corridor that leads to a darkened, empty sound stage. We stop. Twenty yards ahead is a curtain. I see two silhouettes. We wait. Then, that laugh. Tom Cruise is one of the figures behind the curtain. On this side of the curtain two women sit on folding chairs, timing what goes on behind it. One of them gets up and walks over to where I wait with my chaperone. She tiptoes so her heels don't make a noise. She whispers: "In one minute we'll walk you over." One minute passes. They walk me over. I am now on stand-by. The silhouettes rise. There is another raucous laugh and a journalist emerges, beaming. Just then, the curtain is pulled back and Tom Cruise jumps into a playful greeting, adopting a karate-chop stance, inviting me in.

Though he is not a tall man, his personality magnifies his stature. He is wearing black jeans, a snug, long-sleeved dark-green T-shirt, and his small frame is taut and muscular. His eyes seem vaguely, humanly, tired (he's been working since 5am), but his energy is voluminous. In person, as on screen, he is exciting without being intimidating. He laughs easily, makes intense eye contact, and can make an introductory handshake seem like an intimate connection. He has the quality required of any good politician: to make you feel as if there is nowhere else he'd rather be.

We are in a makeshift living room with half-eaten wrap sandwiches on a coffee table between two leather sofas. He gestures for me to sit down and I sit at the end of one, he sits on the other but we sit close, so close I can smell a residue of garlic under the gum he's chewing. Even chewing gum, he seems to exert an intense amount of energy.

Over the years, Cruise has betrayed very little about himself; his interviews are recurring dual themes. He is likable, affable and inoffensive, never irritating or difficult, but he is also extremely careful and remains hidden, guarded and distant. He engages but at the same time is disengaged. His gentlemanly conduct is genuine and also a mask, perhaps a concession for his stringently maintained privacy.

He has taken a break from filming Mission: Impossible 3 to promote his latest film, the Michael Mann-directed Collateral. In it he plays a hired assassin but, because it's Tom Cruise, you still find yourself rooting for him. The character is complex and angry and damaged and flawed; he nails these traits with startling authenticity. In the past he has said: "Acting is finding yourself in roles and bringing aspects of yourself to life." So which aspect of his life is this anger coming from?

"There's not one particular thing. And I gotta tell you, when I do lose it, I don't kick the cat. It's very specific, directed where it should be, and it takes a lot. I'm not someone who just blows their stack." And the last time he lost his temper? "The last time I lost it..." There is a long pause. He looks down, thinking, and fixes me with a look. "I don't lose it, I direct it. Do you know what I mean?

I don't go into a psychotic rage. I'm not like that." He explains he has ways of handling it. He moves on; doesn't analyse. Three years ago, when he filed for divorce from his wife of 10 years, Nicole Kidman (they have two adopted children, Isabella, 11, and Connor, 9), it was said she was shocked at the agility with which he moved on, beginning an immediate romance with his then co-star from Vanilla Sky, Penelope Cruz (which has since ended).

Although Kidman didn't milk it, she won the public's sympathy for his seemingly cut-and-dried departure. But Cruise handles his emotional difficulties privately and, since he doesn't lose it, we have no way of knowing what went on or why the relationship ended. It is in his nature to be pragmatic; if something isn't working and he can't fix it, he doesn't loiter. He overcomes things, even a brush with negative publicity, and he says he is committed to being the one person people can depend on. "I'm there. They know that. Nic. My kids. Anybody,"he affirms.

To begin to understand Cruise, we must understand his need for certainty. He surrounds himself with his family and a small circle of close friends, which includes the directors Steven Spielberg and Cameron Crowe. This year he replaced his publicist of 20 years, Lois Smith, with his older sister Lee Ann, and while reasons for this most likely had to do with exerting control over his privacy and ensuring loyalty, it's possible he also wanted to demonstrate gratitude to his sister. He trusts her implicitly; she will have only his best interests in mind, and giving her a significant role in his life is a way to let her know she's important to him. Now they will protect each other.

Cruise is famously a dedicated Scientologist, and describes Scientology as "an applied religious philosophy" which gives him a code to live by or, as he puts it, "tools" he uses to improve conditions. When you can write your own rules, as the rich and famous often do, having set rules to live by lends a valuable structure. He has often spoken about his childhood: single parent, hard-working mother, moving around all the time, going to 15 different schools and the trauma of always being the new kid on the block in the wrong clothes. Early on this must have led to difficulty, never in one place long enough to find an identity, to allow other children to get to know him, to begin to belong somewhere.Finding out who he was must have taken far longer than it might for the average adolescent.

"Well, it's interesting because you sit in a class, and I remember this, as a kid in Canada - we were in Canada this time - the teacher went in front of the class and whispered a word into the child's ear and the child whispered to the next, and they whispered it and so on. And it went around and came out, at the end, something totally different."

He is making the point that when the teacher deconstructed gossip, she proved there is a disparity between what someone says and what someone else hears. This grey area is most likely something he identifies with. "So you have to recognise that's part of human nature. Especially as a young man growing up, trying to discover who I am and what I want to do. People constantly evaluating you, validating you, trying to define who you are as a person while you're finding out."

Now, as an adult, people are still trying to define who he is, which leads to a great deal of misrepresentation. In the media, for instance. "There's a certain part of it you just have to live with, certain things they're going to say. It became very clear to me when I was growing up that there are certain people who do it on purpose."

It's been reported that his first wife, the actress Mimi Rogers, in an interview she gave to Playboy, said that living with Cruise was like living with a monk, and from that point on, rumours began to circulate about his sexuality. Rogers later retracted her statement - and anyone involved in a divorce understands that unkind and untruthful things are said in anger. Rather than take a passive approach to these rumours, Cruise has vigilantly defended himself legally because he has a low tolerance for unsubstantiated gossip and lies.

Last month he turned 42 but he seems as mystified today by the inconsistencies of life and the foibles of human nature as he must have been when he was in high school. What was it that made him believe life was always fair? "Um, well, I was dissuaded of that as a child. I mean, from very early on, I had an incredible mother and a... fascinating father... but, uh... it was complicated."

He is unequivocal about his mother, but the pause before "father" suggests there is more nuance. "Well, he was a complicated man. You know? He was the kind of person who... he just had a different approach to life." This is where it gets interesting. And characteristically, Cruise is hesitant. It seems he wants to help us understand him, but it is against his better judgment to let us in. But a window has opened, albeit slightly.

Thomas Cruise Mapother IV was born in Syracuse, New York, in 1962. His mother, who he has always described as an "extraordinary" woman, is a southerner from Louisiana who loved being a mother and raising Tom and his three sisters. Not much is known about Thomas Cruise Mapother III. He was an electrical engineer and he wasn't around very much, and Cruise has said in the past that they got close for about one year when he was 10, but then there was the divorce and they were estranged for a long time.

It was his mother who worked many disheartening jobs to keep the family together. When her marriage broke down, Tom became the man of the house and took on the responsibility at an early age. He grew up around women and learnt to be comfortable around them, and is still very protective of his sisters and mother. It is also why he is perhaps less macho than the average American male. But times were tough. They moved constantly. He lived in Canada in the late 1960s, and in 1973 they moved back to the States. They had little money and to earn extra cash he cut grass, raked lawns, scooped ice cream, sold Christmas cards; even as a young man he was never frivolous. He had a seriousness and strong sense of purpose. It seems, too, that he always felt bolstered by helping others, and that a key part of who he is is wanting those around him to do well.

"It's not enough for me to do well," he says. "I got that handled. But I enjoy seeing other people do well. Because I know how tough life is. I know there is no pinnacle of power where you can sit back and rest. Life comes at you, no matter who you are, no matter where you are. Period."

There is no question that he enjoys making people happy. It is why he will spend hours in London's Leicester Square signing autographs, talking on a mobile phone to someone's mother while movie executives kick their heels inside the cinema. He is exactly the guy you'd want in the trenches next to you, because he's exactly the man who wants to be there for you. He is the type you'd want your daughter to bring home because that's who he wants to be. But a bigger picture is emerging. Tom Cruise understands the effects of uncertainty, and the man he wants to be is a man who avoids it at all costs. Cruise didn't speak to his father for four or five years after his parents' divorce; it is reported that they had one meeting before his father died from cancer in 1984.

"There are certain people who can create good effects on others, and there are certain people who create chaos," he says. "My father created chaos. And made it very difficult. So I knew that aspect of it, but then you branch outside of the family and you see the rumours that occur and you gotta go, okay, but then the realisation that, um..." He trails off, unsure of where he's going or if he's willing to go there. I suspect the rumours he refers to are a combination of what his classmates might have said about him, his family, his father, in school, and what the press has written about him as an adult when they have tried to dissect his past. Some imply that his father was an alcoholic.

When asked if he feels he ever got to know his father well, he nods and is purposeful in his response. "Oh, yeah. I feel that as a man and as a father I have a greater understanding and appreciation for who he was as a person."

While he was still alive? "No, after he died, actually. Even before he died I saw him, and you just go, hey, there are certain people and this is the way they are, and it doesn't mean that I don't have to not love them, because I always loved him. He's my father, you know? I can't help caring about him. I just know that in his own way, he had some level of love and cared for me - you can't not for your child. When I became a parent it was like, whoa, man! That's when you call your mom and you're like, 'Hey, y'know, how many times did I tell you I loved you when I was growing up? Well, I want you to know I really, really mean it!'" But the appreciative phone calls go to his mother. Not just because his father is no longer around, but more likely because it is she who earned it. "Just holding my own child broadened my perspective on life," he says.

Like most children, he didn't know how to recognise the impact his parents' limitations would have; how they would play out later on in life, especially now that he too has become a parent. "You don't realise it, you think that's the way life is, but I had a mother who, very simply... the cup was always half-full. Not half-empty. She allowed me to be who I am. "She was raising four kids - and I'd just leave the house. I'd just leave. When I was younger than two years old I'd go for walks. She didn't get me in the house and grab me and say, 'What are you doing? It's dangerous out there! It's a dangerous place! Someone could get kidnapped, get murdered,' you know? She was the kind of woman who said, 'Okay, listen. If you want to go for a walk next time, we'll go together.'

"When I was a kid I broke my nose, broke my fingers, broke my leg - I was jumping off houses, I was climbing trees, I was climbing sides of things. But she was someone who, with everything going on, had confidence that we were going to be okay. And really supported me in things that I was interested in. She was a great adviser to me."

It was a different situation with his father. "There were times when he was an adviser and there were times where he was, uh... he was... he was more frightened of life." Cruise seems to be hinting at something deeper, but again it is vague.

"He was more... you know, he was complex. He was like Heathcliff: he could be brooding, angry, yet there was a romantic quality in him. Uh... it's hard to describe these people in two sentences, aside from my mother, who was definitely the life force. He, uh... he had some problems and he didn't... he didn't know how to solve his problems. He didn't have tools with which he could handle his life and make it better." Did you see it as weakness? "No, I saw it as life. He was my father, so I loved him. But I saw it as, that is life. You know when you're travelling around, there are things that I recognised at a very early age as to who he was. There was a certain level of: I really care about this person but I don't really trust them. I know I can trust my mother. Kids - I don't care what parents say or whatever - they know. If you say to a kid you're going to do something and you don't do it, that means something to them. I never forgot it when I was a kid, so when I grew up and I was a parent, when I say I'm going to do something, I do it. If I say, 'I promise you,' believe me, my kids know it's going to happen. Or, if it doesn't happen - there's a major reason why it didn't." Cruise seems determined to provide for his children something he couldn't rely on from his own father: emotional and physical availability. He doesn't display his kids publicly to prove what a great dad he is, nor does he reveal the specifics of what they do or where they go, but he makes them a priority, whether it's taking a phone call or spending an afternoon uninterrupted. He appears to have amicably worked out with Kidman a way to raise them with a fair amount of stability. Given that his life is filled with activity, there is still a sense that his career is ancillary to his children; not the other way around.

This resolute pledge to responsibility and consistency is the very core of who Tom Cruise is. It is the foundation of his moral code. When, 17 years ago, Cruise's first wife, Mimi Rogers (they divorced in 1990), introduced him to Scientology, an organisation that advocates self-styled "scientific methods" as cures for the body and mind, it was a belief system he connected to.

Founded by the science-fiction novelist L Ron Hubbard, Scientology is widely regarded as a cult, and has been criticised for preying on lost souls, the confused, the depressed, people in need seeking guidance and direction, and then using coercion to keep its members in line. But Cruise is more than just a staunch defender; he feels it is the key to understanding who he is. "You know, if you really understood what Scientology was, you would understand me more as a man."

He says that Hubbard's "teachings" have helped him understand people better, and this is in keeping with his desire to see others do well. "It's looking at someone and going, 'You know what? I'd like to see you do better.' It's caring." He also credits Hubbard's "study technology" with helping him overcome his dyslexia and has given his time and money to Help (Hollywood Education and Literacy Project), which offers this same study technology free to children and adults.

Whatever critics may say about Scientology, it offers Cruise a code that lines up with his own morality. It helps him stay on course and make decisions that he feels are right for him.

But it raises the question: why does Tom Cruise need Scientology? The answer is the same as it would be for anyone who has faith. Because it's what works for him. He doesn't blame his parents or his past, and if Scientology is what helps him tame the chaos, why wouldn't he cherish it? It's reliable, supportive and available when he needs it to be. Perhaps it is the paternal force he never had. And just as a child embraces a parent, he embraces Scientology. Unconditionally.

Even at the very beginning of his career, when he was living in New York and working as a building superintendent, Cruise decided he didn't want to grin his way through life. He had his first big break in 1981, in Taps with Sean Penn. Then, in 1983, he danced into our lives in his white socks and cotton Y-fronts in Risky Business, and has been working nonstop since. He has chosen to work consistently with top actors and directors (Martin Scorsese and Paul Newman in The Color of Money, Dustin Hoffman in Rain Man, Jack Nicholson in A Few Good Men, Stanley Kubrick, Oliver Stone, Steven Spielberg, Sydney Pollack) and he has earned three Oscar nominations along the way. First for his turn as Ron Kovic, the paraplegic Vietnam veteran in Born on the Fourth of July (the anti-war film that he made straight after his Top Gun adventure), again for Jerry Maguire (in which it's been said he ad-libbed the now famous line to Cuba Gooding Jr, "Help me help you"), and most recently in 1999's Magnolia. His performance as Frank T J Mackey in that film electrified and proved that he could channel a dark side. He exquisitely inhabited the role of the male affirmation guru and pitch-perfectly captured the bitter humour. Hearing Tom Cruise deliver lines like "Respect the cock, tame the c***" was strangely liberating.

The human, flawed, ordinary man that resides deep and well hidden in Cruise comes through in many of the roles he's played. But he says in real life he is not afraid of anything, nor is he filled with self-doubt. "That doesn't mean there are not moments where you go, 'Am I handling this right?' But I do have a confidence in myself that I know I'm going to figure it out."

But we don't know much about his feelings, such as loneliness. "Do I ever feel lonely? Sure, of course I do. I'm not filled with loneliness - I have many great friends - but there are certain moments." He looks away.

"I don't know. There are no specific times; there are just moments when you feel, you know..." He pauses. "I'm not a sad, depressed, neurotic, lonely person. But of course there are times - I'm human - there are times when you feel lonely."

Like when? "It's hard to articulate. It's not the loneliness of fame, because..." He lowers his voice and speaks so softly he is barely audible. "Fame opens doors - I meet a lot of people. I have a really full life, but then you go... it would be nice to roll over and have a chat with my girl, you know? At this particular moment I'm dating a movie."

When asked if he misses being married he responds in the positive. "I enjoyed being married. I have to say. Very much. I will get married one day again. Find the person I'm going to spend the rest of my life with. I enjoy being in relationships. I like, uh, that dynamic very much. I like caring for someone in that way." So is Tom Cruise happy? "It's up to us to make ourselves happy. We have a choice about how to live our life. I never bought into 'my life is bad because of my parents'. I've been through some rough stuff and I never thought, 'Well, that's my dad's fault, or it's my grandfather's fault.' A lot of stuff that happened pissed me off and I thought, 'Okay, what can I do to get beyond this?'"

Despite responding affirmatively to nearly all the questions, Cruise is not robotic; he is just careful. He is aware that anything he says can be taken out of context by the tabloids and become accepted wisdom. Admitting he misses being married could so easily end up as "Cruise Pines for Nicole". In many ways he must live as a split personality: one of the most public people in the world wants to be the most private. Who he is remains elusive, and what's impressive is his ability to maintain this impregnable wall.

Our time is winding down, and I ask if there's any chance we can continue for a little longer. He responds to the request for time "to get it right".

"What do you think,10, 15 minutes?" The publicist comes in, and 15 more minutes are granted. But it flies by. We talk more about his childhood and he tells another story that reiterates the theme of being frequently thwarted by the uncertainty of his youth. "I remember dreaming that when I grew up, there wouldn't be any gossip... Then you realise that those social politics are magnified out there and you learn. I've met people from all walks of life - people who have money, people who don't have money. I've had both in my life. And I don't forget any of it. I don't take it for granted." He seems to be suggesting that there was a shift, when he realised that the petty adolescent gossip doesn't go away - it carries over into adulthood (such as the persistent rumours that he is gay); only then it becomes slander, defamation of character and libel. His challenge would be to overcome it, which he has - legally, emotionally, swiftly and privately.

Just then, his sister Lee Ann appears. She is in charge and explains that he has to break it off right away and that he's running behind. There is a sense that if she didn't cut him off, he would go on all night, aiming to please. He came here to do his job, which was to sell the movie, and he could have stuck to a script and toed the line. But he didn't.

So who is the real Tom Cruise? The fleeting glimpses that emerged have revealed a picture of someone who wants to be a better man, to transcend the paradigm of the wayward father and do good. We say goodbye and I feel that I know him a little bit better. But then, he and his sister depart in a different direction and I realise the curtain I was invited behind is a veneer. There was always another curtain and it is behind that one that Tom Cruise has now disappeared.