Before heading to the studio each weekday morning, Paul Newman, who turns 80 in January, and who lives on a farm slightly smaller than Hampshire, likes to take a dip in his local lake. Over the years, his Connecticut neighbours have gotten used to the sight of the World’s Biggest Movie Star calmly strolling up the side of Route 7 clad in a towel, accompanied by three or four of his pedigree, award-winning Dobermans. Newman himself seems a prime specimen of an unusual breed of alpha male – the happy warrior who comes equipped with a soul and a sense of humour. During a fifty-year career, he’s demonstrated a remarkable talent for making vast amounts of dosh for himself, his co-stars and the studios, and for living by a simple set of rules: don’t stray far out of character, get along with the suits, keep the overheads low, be philanthropic and have fun with what’s left.

Paul Leonard Newman was born on 26 January 1925, the younger of two sons of middle-class parents in a suburb of Cleveland. His formative influences were his pushy, stage-struck mother, a hitch in the US Navy and – largely for the opportunity to meet girls – the Actors’ Studio, followed by summer stock in Boston, where he shone in such otherwise forgettable fare as All My Sons and Dear Brutus. Armed with intelligence, ambition, pride and a pair of eyes as blue as gas-jets, Newman would launch himself by way of 1955’s heavy-handed epic The Silver Chalice. Despite the handicap of this unintentionally comic screen debut, he went on to dazzle as Rocky Graziano in the biopic Somebody Up There Likes Me (1956); in short order he was ‘doing’ Billy the Kid in The Left-Handed Gun, winning the best-actor award at Cannes for The Long Hot Summer, and scoring his first Oscar nomination for Cat on a Hot Tin Roof – all in the same year. A star was born.

Somebody Up There was also the blink-and-you’ll-miss-it film debut of a 26-year-old hustler playing the bit part of Fidel – ‘a blade-wielding punk’ as the credits put it. From then on, Newman’s career became a kind of pace car for Steve McQueen’s. Somebody’s director Robert Wise is only the most compelling witness to the fact that it was ‘undeclared war’ between them, two physical types whose all-American qualities inspired entire PhD theses, not to mention Erica Jong’s orgasm in Esquire. The feud reached its own climax when the two superstars came to debate their billing, eighteen years later, in The Towering Inferno. A compromise was agonizingly reached whereby McQueen’s name would be on the left, and Newman’s a shade higher, exactly a foot to the right, on the marquee. That twelve-inch gap was a 25-year rivalry in miniature.

In 1965, McQueen emerged from semi-retirement to score half-a-million dollars and critical raves for The Cincinnati Kid. In terms of pacing, locale and overall theme, it was a transparent reworking of Newman’s 1961 vehicle The Hustler. Both performances were gently nuanced, particularly in the dopey ways the Paul and Steve characters related to their women – in stark contrast, it has to be said, to real life, where both seemed to pass most of their thirties with a four-alarm fire in their jockey shorts. Citing infidelity, Newman’s first wife divorced him in late 1957; a fortnight later he married the actress Joanne Woodward – they’re still together today.

Reciprocally, Newman’s Cool Hand Luke (1967) was squarely in The Great Escape’s tradition of authority figures versus heroic screw-ups, something of a Hollywood fad at the time. The genre swung to its zenith two years later with Butch Cassidy and the Sundance Kid. Here the original plan was for McQueen to play the Kid – on the understanding that he have top billing, or that they quite literally toss a coin for it. After Newman baulked the studio first thought of goosing the movie with Marlon Brando, then gambled on a 31-year-old underachiever, name of Redford. It would be the perfect family entertainment: Paul ‘n Bob for the ladies, quick-draw action for the guys. Newman was brilliant, even McQueen later conceded.

The faultlessly liberal Newmans almost seem like a Hollywood cliché in 2005, but thirty or forty years ago they walked virtually alone: when not busy being the top box-office draw in the world, Paul found time to speak out against nuclear arms and Vietnam, and for equal rights and abortion. (He famously made the top of Richard Nixon’s ‘Enemies List’ in 1973). He’s also been the most charitable of superstars, forking out millions (part-financed by all those salad dressings and sauces) to such worthies as Catholic Relief Services, the Fresh Air Fund and the anti-drug Scott Newman Center – founded after the overdose death of his only son.

Meanwhile, Newman would remain (and remains) in the saddle years after his highly-touted contemporaries succumbed to self-parody or worse. Absence of Malice (1981) had something genuinely of interest to say about the media, as did The Verdict (1982) of the so-called American justice system. At a time when most blockbusters already competed to limbo under the bar of their own gleefully low standards, these were two that dared to be literate. And Newman was on song throughout: after half a dozen near-misses, he finally won the Oscar for The Color of Money (1986), in which he reprised Eddie Felson from The Hustler. Despite the thirty year wait, he cheerfully told the Academy that they could send him ‘the fucker’ in the post. They did.

‘The thing about Paul,’ Robert Wise told me, ‘is that he’s brighter than the average star. I’m not damning him with faint praise. The guy’s just masterly in choosing roles – I mean, Nobody’s Fool, Road to Perdition. Whatever he does will go.’

It will ‘go’, Wise believes, because ‘Paul’s heartfelt, not phony-baloney. He doesn’t act for his ego; he acts for the service of the piece.’ Which is why as many as a dozen Newman flicks are up there in the All Time Greats. Even fifty years ago, there weren’t too many actors around who could do the tough-but-tender bit as he could. Of today’s airbrushed crew, perhaps only Johnny Depp comes close to pulling off the same sort of unselfconscious charm, combined with a hint of menace.

It’s this that I hate more than anything else about modern Hollywood: the way nearly everyone and everything has to be fluffed and puffed to make reality better and smoother and cooler than it really is. It’s evil, and when Bush appoints me Culture Czar I’ll have it stopped. Then we can all go back to watching Hud and The Secret War of Harry Frigg.

Christopher Sandford’s McQueen: The Biography (HarperCollins) is available in paperback.