THE DAY before I meet Sir Tom Jones, an e-mail is sent to me outlining subjects that will terminate the interview. Knicker-throwing. (Top of my list, obviously.) Infidelity. (Reputedly top of Sir Tom's.) And cosmetic surgery. (Oh, sorry. Was I not supposed to mention that?) Jones turns out to be rather bigger than this instruction but, still, it's a pithy little life synopsis for the sex-bomb superstar so beloved of the laydeez. Although, obviously, he's a respectable 65-year-old knight of the realm now.

It's always instructive to politely enquire of knights if they prefer to be called Tom/Dick/Harry or Sir. Not that I have any actual intention of bending the knee, but it's very revealing. "Oh, call me Tom/Dick/Harry," they always say, some with more convincing insouciance than others.

"Hello, love," says Sir Jones, the accent still pure Pontypridd. "Tom's my name, but either's fine." He shakes hands. He is dressed all in black, with a Victorian villain's black beard and moustache, and black, wiry hair. He is not tall; the impression is more of powerful-shouldered breadth than height. And, clearly, he has drunk a lot of Tango in his time. But a kind of down-to-earth warmth emanates from more than his orange glow.

Trying to interview Jones without asking about women would be a bit like trying to chew meat without teeth. Impossible. Yes, he became known as 'the Voice'. But he also became known as a stud. Both sobriquets implied more power than subtlety. Now, the PR men want to airbrush the knicker-throwing reputation because it traps him in a timewarp. "I never realised the image might get in the way," admits Jones. "I thought it might enhance it." Was he ever really that hard-drinking, hard-living man who loved women? "Yeah," he says with deadpan humour, then laughs. "Isn't every man?"

His sexuality was so overt - a kind of male Jordan - that it became more turn-off than turn-on. It was a bit like being presented with a two-pound bag of sugar instead of a box of chocolates - too unrefined, even for the sweet-toothed. But when Jones's manager, Gordon Mills, who had steered him from his first number one - 'It's Not Unusual' - in 1965, died, Jones's son Mark became his manager. Out went the 1970s chest hair and gold chains and in came a reconstructed Jones, one who collaborates with hip young musicians. A recording of the Prince classic 'Kiss' with Art of Noise revived his career. Then came Reload in 1999, a well-received album of duets that included his mega club hit 'Sex Bomb', and an album with Wyclef Jean in 2002 called Mr Jones.

His latest single, 'Stoned in Love', is further evidence of a chameleon-like ability to change the colour of his musical skin. A collaboration with 27-year-old Nick Bracegirdle, better known as Chicane, the song has vintage Jones power vocals in the chorus. But few would recognise the voice opening the song. "I wanted him to do something fresh, different, to sing in a way that is newer," explains Bracegirdle, who, despite pop being a forward-looking industry, had no qualms about working with Jones. "It's a huge voice he has got, but he has also got charisma somehow. Everyone kind of respects him. It's like when he was doing the Brits, and Robbie [Williams] was gushing all over him. He's like the godfather of singing, and to work with him is pretty special."

Jones's career is interesting for its evolution. His private life is interesting for its consistency. He has been married to the same woman for almost 50 years. That fact is rather more intriguing than the allegedly endless affairs. So the international superstar got offered a different dish every night and opted for the smorgasbord? Well, knock us all down with a chorus girl's feather. When he lost a paternity case after fathering a child with a 24-year-old model in 1989, Jones paid up, though he was quoted denying responsibility still - the test was only 99% accurate. His marriage survived. Jones's marriage has always survived.

He married Linda Trenchard when they were both just 16 and Linda was pregnant. Reading through the cuttings, I become fascinated by Lady Linda. She seems to disappear round about 1969. She gave interviews with her husband then, but in later years is only referred to as a reclusive television addict who refuses to go out or meet people. Snatched pictures are unflattering. As the years roll on, the cuttings become stranger. The bigger Jones gets, the more she shrivels. It's almost like Mrs Rochester hidden away in the attic. Mrs Jones hidden away among the gold taps and air-conditioning of a Los Angeles mansion. Or is that a media invention? Who is Linda Jones really? And what are the extraordinary ties that bind her and her errant husband together?

LINDA TRENCHARD was bending over playing marbles when Tom Jones first saw her. "I saw these legs. She had great legs." His eyes glint; the lips break into a smile that holds a whisper of a private joke - a smile that says whatever picture reel is playing in his head right now doesn't crackle only with age. They went to different schools because Jones was Presbyterian and Linda was Catholic, but met in the street. (Jones still believes in God and is still Presbyterian. Fewer rules, he claims. The Jones version, anyway.) He was ten when he first gazed at Linda's legs. Sex bombs, it seems, explode young.

So what is Linda really like? "Well, she's a shy person. She is reclusive... She doesn't like that word, so I shouldn't really use it, but she knows she has a depression problem if she doesn't watch it. But she talks about it and says it runs in her family. Her father was a bit like that, apparently, and her grandmother. Sometimes she can't go out, or doesn't want to meet people."

Depression can be hard to understand for those who don't share it. Jones accepts it. "I don't force her. It's hard sometimes to get her to a check-up or something, to go to the doctor, because she doesn't like doctors. That's the way she is. She has had it since she was a child, apparently..."

Perhaps it suited him in a strange kind of way, the negative to his positive, the complete separation of public and private. But he rejects the suggestion that Linda is a victim of his success. "No, no, it's just the way she is. She doesn't like to get older. Really doesn't like it."

Isn't that hard for Jones too? His fame has been based on a physical voice and sexual virility, both affected by age. He seems unthreatened by the question. "I understand exactly what you mean. But it doesn't come up. I'm working with young musicians and they never say anything. If they do, it's complimentary... 'Jesus Christ, how come after all this time you still have the passion for the music?' Some of them get tired."

Being an extrovert married to an introvert must surely be difficult. "Not really, because when we are talking together you wouldn't know. I was talking to her on the phone last night and she said, 'How's it going over there?' I said, 'Great,' and she was, 'Oh, great!' And I thought to myself, 'If someone was talking to you on the phone, they would never think you were reclusive.' She doesn't sound it. It's just getting past that nervous thing she has with many people, but she doesn't have it with me."

When they were children, Jones contracted TB. He didn't feel ill after the first few weeks, but was confined for two years - from the ages of 12 to 14. "I used to draw a lot. I think maybe without the voice I would have become some kind of artist, but the voice took over." The drawing diminished when he was allowed to sing again. "It was a strange time to be locked up. You're going through puberty, you see."

Maybe just as well he was locked up? He smiles. "Maybe so. As soon as I got out I got with Linda, and she got pregnant - maybe it was because I'd been confined for that bloody long!"

Singing defined him. It always has. Jones wasn't academic. He wasn't sporty. He was the boy with the big voice. "It gave me confidence that I had something." Otherwise, he might have lacked self-esteem. "I heard recently that some people who were not very good at school say they are dyslexic to pass it off, but I think I was. I know for a fact that even a word I can spell, I can start in the middle of it for some reason and have to backtrack. Or I'll leave letters out. There's definitely a problem. It's not just that I'm thick," he laughs.

Performing came naturally, schoolwork didn't. He loved Welsh parties because of the singing. His father had a voice, but needed to be coaxed. His mother was a performer, but knew she didn't have the voice, not really. But Tom, he was always dying to get up there. "When are they going to ask me?" he would whisper to his mother.

His mother was the centre of his universe. He had one sister and was surrounded by cousins, but it was his mother he gravitated to. "If Mam wasn't there when I came home from school, it was, 'Where's Mam?' If my father wasn't there, I knew he was either in bed, at work or down the club. I just took that for granted - he was somewhere. But my mother, where was she? I'd go round looking for her down the shop."

It was a traditional household, another reason why Linda's lack of career ambition suited him. I quote to him from an old interview, in which he derided career women and added, "I like an intelligent woman to talk sensibly about the world, but I think she should always know her place." A sticky wicket, surely, even in 1969? "I didn't say that," he protests. But I have the cutting in my bag. He was misquoted, he insists. All he said was that he was brought up to believe that the man went to work and the woman kept house. "That's how it was in my family. But to each his own. It all depends on who you are and what works for you. But in my family that's the way it was. My mother liked it that way and my father liked it that way. They weren't forced."

His mother was a strong woman, like his grandmother, and very houseproud. "She was always bloody painting and decorating and was very proud that we had this lovely wee house."

His father, a coalminer, was fiercely patriotic. "Our family name was Woodward, and I used to bring it up a lot. I would say, 'Why does Nana speak funny?' And my father would say, 'She's not from here.' 'Where's she from?' 'England.' 'Why is that?' I was one of those kids. I said, 'If your mother's English and your father's English, you're English.' He said, 'I'm not English, I'm Welsh. I'm a Welsh coalminer, that's what I am.'"

Jones's aspirations were a million miles from the mines. He always believed he would be a singer. Despite a hard-drinking reputation, the desire to perform kept him sober. His drinking has always been social. "I don't crave alcohol and never have." Gordon Mills could never understand why Jones went to pubs - surrounded by idiots! - instead of drinking at home. "They're not idiots," Jones would tell him. He liked bars. He liked people. "I like talking," he grins, "as you have no doubt discovered."

But drinking was less important to him than performing. He remembers buying a house in Los Angeles that had belonged to Dean Martin. "It had two bars, and I thought to myself, 'Christ!' When I was a kid and saw that in the movies, people drinking at home, I thought that would be something, a bar in your house and crystal glasses, able to have a drink whenever you wanted it. Well, it so happens that you can't," he says. "Your voice doesn't work if you have drunk too much - mine doesn't, anyway."

He never needed Dutch courage to perform, never needed a crutch. Unlike his friend Elvis, who used to ask Jones how he dealt with success. "I said, 'I enjoy it.'" But what drug did he take to keep him sane? "I said, 'I don't. Maybe that's one of the reasons I enjoy it.' Elvis said he had tried everything, but he didn't say he was still trying it. He wouldn't admit that to me."

They lived different lives. Jones told Elvis that he could live normally if he stopped drawing attention to himself. Did he need an entourage? Were white rhinestone suits the most inconspicuous garments to wear? "But I think he liked being Elvis Presley."

And does Jones like being Tom Jones? "It becomes part of you, and there are more advantages than disadvantages." This week, for example, he has been jetlagged. He couldn't sleep and felt grumpy. "Then I thought, 'Wait a minute, what have you got to do when you get up? It's only Top of the Pops, only one song, for Christ's sake.' It's not like most people, who have to work a full day in a factory or on a building site. Then you can say you've got a bloody full day of hard work, not just singing one song or doing an interview. So I check myself then."

He has no celebrity pretension. "A lot of showbusiness people think they have to be with people who are hip enough to be seen with, or cool enough... I'm not like that." In the 1970s he used to hang out with Jimmy Tarbuck. "There was no bullshit with him. He came from the same background as me and felt lucky to be in it."

But he also counted Elvis as a true friend, not just an acquaintance. "I was in a house in Hawaii he had rented once, and we got on great. He wanted to tell all these people round him that he really liked me." Jones adopts an Elvis voice. "I just want everybody to know that Tom Jones is not only a great singer, but a good guy..." One of the crowd said, "When are you two getting married?" Everybody laughed, except Elvis. "He really meant it. He was trying to get a point across."

Did he ever feel guilty about not helping Elvis more? "Only when it was too late. He was crying out for help, I suppose, but if people tried to tell him he had a problem he would fire them."

Elvis's close friends were Red West and his cousin Sonny. "Sonny West came to see me and said, 'We're worried about Elvis. We can't get to him. But we're sure you could.' I said I would try. But he wouldn't answer my calls. Then he died. You think, 'Maybe if I had pushed a bit harder, tried a bit more...' I saw Red West a couple of years ago and he said, 'We all thought if anyone could have got to him it would be you. He genuinely liked and respected you.'"

While Elvis surrounded himself, Jones has relied on one close adviser. First Gordon Mills, then his son Mark. It was a natural progression for Mark, who had been on the road with his dad since he was 16. People wonder how your son can be your manager, but Jones always respected Mark; there was never a bossy-father-subordinate-son relationship. He was away such a lot when Mark was young. This has been a chance to be together. It was Linda's idea. But I read that she was heartbroken at her son being taken away? "No," he says. "She suggested it."

It is the moment to tear up that PR instruction. He is clearly close to Mark; wouldn't he like that relationship with his other son? Tension descends. Jones's PR shifts suddenly in his seat. "No," says Jones. "I don't talk about that." But the way he talks about Mark... "Oh, yes, but he's my wife's child," he says, and the phrase says everything. There's a love child and a sex child. Tough on the sex child. It sounds breathtakingly callous, but maybe that's the primary rule binding Tom and Linda Jones. Don't confuse casual sex with love. Acknowledge a son; lose a wife.

Despite everything, his relationship with Linda has been the affair of his lifetime. "Definitely," he agrees. What has kept them together? "Love, I suppose. And we've always liked one another. We have a similar sense of humour because we come from the same place. I think that has a lot to do with it." Has he ever come close to falling in love with anyone else? "No," he says. The word is instant and insistent.

ONE question stumps Jones. Why did Linda fall in love with him? Silence. "No one has ever asked me that before." He stalls. "I know why I fell in love with her... the marbles, like I told you... the legs... but I don't know. It's a good question, because all the boys were after her. She was very pretty. You know what she said last night on the phone? She said, 'I'm proud of you.' And I said, 'Thank you.'" His voice is quiet, almost humble.

Maybe the fact that Linda loved him before he was famous matters. "When I've got drunk in the past and we've argued, she has said, 'Well, I didn't bloody marry Tom Jones. Don't forget that. I married Tommy Woodward." It keeps him grounded. "Some people don't want to be grounded and won't take it. I'm not like that."

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