Take the first flurry of shots. On the soundtrack a tickertape ticks. A tank crashes through a book-lined study, heralding the King's assassination some time in the 1930s. Earl Rivers flies in from America. During victory celebrations in a palace ballroom, Ian McKellen's Duke of Gloucester takes the band singer's microphone. But instead of singing he soliloquises: "Now is the winter of our discontent, made glorious summer . . ."

Limping through the crowd, this oleaginous charmer with the thin moustache (think Hitler, think Mosley) beckons us and the camera to follow him. We end up in the gent's toilet, the soliloquy still flowing. Shakespeare was never like this before. Even Richard Eyre's 1990 National Theatre production, the film's inspiration, was never like this.

The energy is overwhelming. Much of it stems from the telescoped script: what can last four hours on stage now takes 103 minutes. McKellen sends up his own shower of sparks. Transposing Shakespeare's disfigured schemer to the decade that appeased fascist dictators may be an obvious trick, but McKellen's force keeps the characterisation valid. Speaking to others, this murderous usurper in black military uniform coats words with jam. Speaking to us, straight to camera, out come the smirk, the scowl and the conniving glint. This man, you feel, is truly dangerous.

And yet the film might still have trundled along, half theatre, half cinema, with a director other than Richard Loncraine. Experienced in television and commercials, Loncraine is uninhibited by reverence for the text or the sight of great actors in flight. He pushes the images along like a speed demon; and if some of Shakespeare's words jar in context ­ "My kingdom for a horse!" Richard cries as his Jeep is hit ­ then it's just too bad.

Indeed, collisions between text and image are part of the film's jaunty appeal. Here is Lady Anne (Kristin Scott-Thomas) going to hell the modern way, injecting heroin into her thigh and smoking rolled-up banknotes. Here are Annette Bening and Robert Downey Jr lounging like tourists as Edward IV's American wife and brother-in-law. Locations and computer simulations provide amusement of their own. Edward rules from the Gothic exuberance of a riverside St Pancras, while Richard prefers the cold marble of Senate House. As for Bosworth Field, site of the final battle, that becomes the burnt-out shell of Battersea Power Station.

Shakespeare's words are cut to the quick but otherwise unaltered, apart from the odd rebuke by Richard's chauffeur to a kid jumping on the car's fender. Loncraine's actors vigorously pitch into the charade; with Jim Broadbent as Buckingham, Maggie Smith as a horrified Duchess of York and Nigel Hawthorne as the gentle Clarence, you are guaranteed tasty moments. This may not be the most thoughtful Shakespeare production around; but it certainly makes for rip-roaring cinema.