ΒιΆΉΤΌΕΔ

Al Gore is an unlikely movie star. Earnest, tubby, and frog-like, he carries even now the faintest aura of defeat, like a persistent limp. His movie debut, An Inconvenient Truth, is not a drama or even a documentary. It's a slide show, delivered to a live audience, on the subject of the environment. Doesn't sound too thrilling, does it? And in truth, it ain't Die Hard. But be assured: this a really really good slide show.

Gore has been around the world with his presentation, and he's got the patter down to a fine art. Over the course of 90 minutes he explains, in simple but unpatronising terms, just how very badly we have screwed up the planet. There are diagrams to this effect, although they all seem to show the same, alarming image: a single line, climbing towards disaster. It's not as depressing as it sounds - no, hang on, it is as depressing as it sounds, but Gore is an engaging host nonetheless. His shucksy southern drawl is comforting, but beneath it lies a sense of humour that's as dry as a Martini.

"GET BACK TO THE SCARY PIE CHARTS!"

It's an enduring irony of movies that one guy talking can be more compelling than a million dollars in locations, extras and effects. Director Davis Guggenheim hasn't quite learnt that lesson and chooses to intersperse the fascinating lecture with annoying shots of Gore being wistful, or concerned, or noble. We delve, briefly, into our hero's family and career, but it feels like a distraction. "Get back to the scary pie charts, Al!", we cry. That aside, this is a useful film about a vital issue, arguably the most vital of them all.