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One of the great grudges luvvies have against the film industry is that it steals the lifeblood of theatre and gives back next to nothing. Then along trots a film like John Madden's Shakespeare in Love with the most thrilling, sentimental and hilarious plug for the stage that I have ever seen, and suddenly luvvies the world over are delighted. This, presumably, is because half of them seem to be cast in it.

There is plenty to be thrilled about. If you don't look deeper than the words "romantic comedy" you'll find a ripping yarn about a struggling, upstart scribe called William Shakespeare with serious quill problems: sexual as well as inky. Not only is he suffering chronic writer's block, but he hasn't had sex since he ditched his wife in Stratford months before. "It's like trying to pick a lock with a wet herring," says Joseph Fiennes's depressed Will, limply throwing himself on the couch of Antony Sher's quack psychiatrist.

A muse is what Will needs. Someone to get the juices flowing so he can start his epic, Romeo and Ethel, the Pirate's Daughter, for Geoffrey Rush's seedy theatre owner, Henslowe. Inspiration is at hand. During the audition from hell with the usual stutterers, dwarfs and drunks, Will bumps into Gwyneth Paltrow's rich, stage-struck Viola, disguised as Tom Kent, who duly lands the role of Romeo. Their secret affair blooms through moustaches and tights, and Will suddenly finds his first major masterpiece flowing from his quill.

The magic of this beefy romance is that the play not only maps their lovelife, but races ahead to plot their destiny. But the sly genius of the film is the way the writers Marc Norman and Tom Stoppard bring a thoroughly modern sensibility to the daily pitfalls of theatre folk in the Renaissance. It's the Blackadder/Monty Python factor. The mean streets of Southwark are close, mucky and claustrophobic. People are routinely splattered with pots of urine. Feuding playhouses fight for the same impoverished, plague-ridden audiences. Writers are two a penny. And the Thames is crawling with ferrymen who say "I had that Christopher Marlowe in my boat once."

Colin Firth is the only real villain. Wonderfully grumpy, he is naked self-interest buttoned into the dastardly Lord Wessex, who has earmarked Paltrow's hand and fortune with the blessing of the Queen.

"Too late" mutters Judi Dench's terrifying monarch when half-a-dozen fur cloaks hit the puddle she has just waded through on her way to her coach.

The irreverent joy of Shakespeare in Love is that it's knocked into shape by a series of accidents. This is vintage Stoppard. Normally, as in Arcadia, he places some jaded scholar at this end of the millennium to field these accidents and wrap them in some sort of academic fallacy. Here the fielders are us and, no, we don't want to do any intellectual stretches because we like our greatest cultural icon to look like the foolish, infatuated human being we hope he was.

There are romantic niggles. Is Paltrow more infatuated with the poetry than the man? "I love you beyond poetry" is the most insincere line in the script. Yet, dressed as the vulnerable Romeo, or undressed as the sensuous Viola, Paltrow delivers the most convincing and mesmerising performance of the film. Fiennes's Will is magnificently moody. The studied tilt of the head, the hairy glimpse of cleavage, the smouldering stare are things few would dare to attempt even in the privacy of their own bathroom. But he doesn't sink many boreholes of illumination into the Bard.

For all the chest-beating about theatre, this is ultimately a victory for film. Director John Madden may have innocently set out to martyr a few sacred theatrical cows. What he actually ends up with is a sophisticated 16th-century spin on Robert Altman's Hollywood satire, The Player. If more films were as revealing about the haphazard magic of theatre I'm not sure there would be much theatre left to watch.

The luvvies may have a point after all.

15, 123 mins

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