First Night: Brüno, Empire, Leicester Square

Out of Austria: Brüno storms London

Most people who watch Brüno will snort with laughter at the jokes, gawp in disbelief at the outrageous stunts, marvel at the star's physical comedy prowess and death-defying bravery ... and still leave the cinema disappointed that it wasn't done better. (EPA)

If intimate waxing, full-frontal nudity, Mexican "chair-people", jokes about Hitler and pygmy sex involving an exercise bike, a champagne bottle and a dustbuster make you uncomfortable, then Bruno makes for a pretty uncomfortable 90 minutes. So for most people, this will be less a popcorn movie, more an open-mouthed, watching-from-behind-your-hands movie.

Sacha Baron Cohen’s latest character, a gay Austrian fashion reporter called Bruno has been difficult to avoid of late, descending from the ceiling of the MTV Movie Awards to land - bare buttocks first - on a furious Eminem’s face and stripping off for GQ to reveal a buffed body to make Jennifer Aniston jealous. But if his ubiquity and popularity now mean that everyone is in on the joke - the MTV prank was planned with the rapper's permission - it's still a pretty funny joke.

For the London premiere Baron Cohen walked the red carpet in Bruno's inimitable take on national dress: namely a towering bearskin, perched jauntily atop bleached blonde hair, cropped red guardsman's jacket and black leather hot pants. Introducing the film he announced that he hoped it would "undo all the negative stereotyping of the gay community done by Milk [about the gay rights activist Harvey Milk] in which the lead actor wasn't even gay."

For there have already been rumblings of concern that Bruno, rather than exposing and ridiculing homophobia (in the way that Borat lampooned anti-Semitism) might actively encourage it. While Baron Cohen used the fact that he is Jewish to deflect criticism of Borat, the fact that he is heterosexual makes Bruno a more troubling prospect. In fact, the homophobes in the film are so utterly ridiculous - the creepy "gay converter" and the anti-gay marriage protester who gets tangled up in his own "God hates Fags" banner when Bruno comes running at him in the street, naked and chained to his assistant in a bondage harness - that this will surely not be the case. The sexuality of Bruno is only one strand of a film in which Baron Cohen embarrasses, without a trace of squeamishness, everyone from pushy mothers to vacuous celebrities, belligerent television viewers and charity parasites.

Bruno is the host of "Funkyzeit", "the most important tv fashion show in any German-speaking country. Except Germany". Shunned by his home country after disgracing himself at a Milan catwalk show, where he literally brings the house down thanks to a destructively sticky velcro suit, Bruno sets out for L.A to become "the biggest Austrian superstar since Hitler". His path to fame takes in acting, an abortive attempt at a sex tape (with former Republican presidential candidate Ron Paul, no less), founding his own charity ("Darfur is sooo over. What's Dar-five?"), brokering Middle Eastern peace and adopting an African baby.

As with Borat, there are several, occasionally familiar, set pieces, all breathtaking in their guile - dressing his adopted son in a cropped top emblazoned with "gay-by", an explicit swingers party and a climactic cage fight which transfigures into a tender all-male love scene in front of a baying mob. But unlike Borat, the lines aren't blurred enough. Bruno and his exploits are too outrageous and, particularly in the light of the Eminem episode, no longer believable. Without the worrisome, compelling ring of truth, these big scenes drag a little.

He's better at the smaller jokes, when he reins himself in a little. There's a brilliant moment when he confuses Hamas with humous during peace talks and a fabulous baby audition montage. Watching Bruno trying to blend in as an extra is a joy as is his tv magazine show, which includes an item discussing the famous foetuses of pregnant celebrities.

The film ends with a charity record for which the great and the good come out to parody themselves as they've done before on Comic Relief and Ricky Gervais' Extras. This unoriginal finale feels like Baron Cohen's last big blowout, an indulgent if deserved goodbye to a triumphant trilogy of spoofs - Ali G, Borat and Bruno - which have now, surely, reached the end of the line. Still, I can't wait to see what he does next.