Nixon begins inevitably - and unimaginatively - with the Watergate burglars about to embark on a disastrous night's work. All very Oliver Stone. The next shot, however, is different: the White House bathed in the crepuscular sheen of a violent storm, the Stars and Stripes flapping wildly in the squall. This is no longer the symbol of the Free World; this is no Independence Day. The aliens will not destroy this White House from outside, but, as President's aide John Dean explains, as a cancerous growth from within. The shot is pure Hammer, the Gothic mansion on the hill. Except no Vincent Price this time around, it's Anthony Hopkins as the monster.

But there is the rub - neither is Hopkins quite the brute we expect. He's a mad man, because we all know that Richard Milhouse Nixon was a mad man. As Tricky Dicky he was very probably evil. But the Nixon of Oliver Stone's overfed epic is as much abused as abuser, a loud-mouthed but ultimately pathetic little man haunted by a strict Quaker upbringing and the beast he feels stalking his every move. "Thou must find thy peace at the center," his mother Hannah tells him. "Strength in this life. Happiness in the next."

The film is made in what, after JFK and Natural Born Killers, we can readily identify as the Stone-style. It's no straight biopic, and plunges its audience immediately into a barrage of names and dates. The BBC's essential series on Watergate took something like four hours to tell much of the story Stone thwacks us with in about ten minutes flat. The initial half-hour is pyrotechnic and confusing.

The remainder is no less pyrotechnic but evens the picture out in a lucid, absorbing, not-over-long three hours plus. Stone is using his whole magic box again, everything from orthodox (one might even suggest dull) framing/colours, through immoderate lighting effects and camera angles, degraded and black and white film-stocks and newsreel. Toss in some nicely used time lapse and typically taut editing, and it's JFK 2: The Republican Empire Strikes Back. You are not about to get bored with this film visually or structurally. Only the monochrome childhood flashbacks wear thin, much as the family-life of JFK tested one's patience. Stone never has been good at that stuff - too many women, perhaps?

Nixon is nothing if not a boy film. There is wheelbarrow-load of top-notch playing from the likes of Ed Harris, E.G. Marshall, David Hyde Pierce, and Powers Boothe as the always sinister Alexander Haig. Better yet, Paul Sorvino's Kissinger is a virtuoso turn, James Woods makes for a sinewy H.R. Haldeman, and the great J.T. Walsh has never been better than he is essaying Ehrlichman for Stone. Outside of the White House we get Bob Hoskins' camp, ogreish Hoover and, surprise, a notable Larry Hagman cameo as a sinister businessman.

In the end though the film stands or falls on Hopkins, and Hopkins here is outstanding. Seldom off screen, he disappears into this nervy, sweaty, wretched little man's skin, squaring the jaw, occasionally making him sympathetic, but never loosing sight of the poison in his heart. Joan Allen's Pat Nixon is there to lend our anti-hero emotional support, but makes far more of the part than it initially offers.

Nixon was a difficult man, of course, and even at three and a quarter hours the film can barely scratch that surface. We remember him as cunning and corrupt, and so he was, even if his political legacy - ending Vietnam, opening up Red China - is arguably better than that of his archenemy Kennedy. The film, to its detriment, skirts over much of road that took him to the White House, notably his crucial role in the HUAC.

Stone might have been expected to damn out of hand, but there is sympathy in these frames, one that doesn't excuse but does try to explain. "You can't stop it," a protester says of the war. "Because it's not you. It's the system. And the system won't let you stop it..." In the end, this Nixon's villainy is Shakespearean: "They need to sacrifice something, y'know, appease the gods of war - Mars, Jupiter. I am that blood, General... All leaders must finally be sacrificed."

This is Oliver Stone, of course, and so the film is too long, too loud (odd how John Williams writes his best, least bombastic scores for Stone) and too didactic. But it is also intelligently written and compellingly played. Its flaws are manifest, its overstatement carried through to a video sleeve that, bizarrely, seems to be going for that Independence Day look, replete with explosions and Nixon himself hovering menacingly over a tiny tiny White House. But it is also an uncompromising, enthralling three hours of truly epic American cinema, and these days not too many can lay a claim to that.