(MA15+) **

Director: Todd Phillips.

Cast: Bradley Cooper, Zach Galifianakis, Ed Helms, Justin Bartha, Ken Jeong, Mason Lee.

A JOKE is never as funny the second time around, no matter how hilarious it was the first time. So no matter how great The Hangover was, it was always going to be an uphill challenge for the sequel to match it - every time a character in this follow-up groans "I can't believe this is happening again", you can only nod forlornly in agreement.

Phillips and company have stuck devoutly to the structure of the original, just replacing basic elements. Instead of Doug (Bartha) being the groom-to-be, it's Stu (Helms). Instead of waking up in Las Vegas with the mother of amnesiac hangovers, it's Bangkok. Instead of finding a tiger in their room, it's a drug-dealing monkey. Instead of Stu waking up with a missing tooth, it's a facial tattoo. Instead of the plot revolving around a search for the groom, it's the groom's future brother-in-law (Lee). Instead of Mike Tyson singing In The Air Tonight, it's One Night In Bangkok. And so it goes....

In an effort to top its party-to-end-all-parties predecessor, The Hangover: Part II pushes for darker and harsher. If you thought marrying a hooker was bad, wait until you see what the ladyboys of Bangkok can do to our duntish trio.

There are still some funny lines and moments, but the sequel reminds you that it was the mystery of the first film's plot that made it so interesting. Second time around, the mystery is dissipated and you find yourself wondering less about what will happen next to the heroes and wondering more about how far they are willing to push the envelope.

Thankfully, the script is unapologetic about its bad behaviour, which was another secret to the first one's success. It's refreshing for a film to be so low on moralising, choosing to say, "You know what? This is what happened. If you don't like it, f*** off" rather than getting to the end and going "You know what? I learnt something today....".

Galifianakis's petulant loose cannon Alan is a welcome return and gets most of the best lines. A scene in which he uses meditation to try and recall the events of the previous night is a highlight. And who doesn't like monkeys?

But the biggest problem is that The Hangover is just not as funny second time around, and this feels like a remake. You do have to admire the "if it ain't broke, don't fix it" approach, but it just goes to show that comedy doesn't work as well in a retread formula as, say, the James Bond movies or horror films. Other issues: the cause of the memory loss is disappointing, a serious debilitating life-changing injury to one of the characters is pretty much dismissed, and Chou is back, more annoying than ever.

The Hangover: Part II is likely to be a box office hit, if only because people will want to hang out with Stu, Phil and Alan again. That will most likely mean a third film, which I predict will involve the Wolf Pack heading to Amsterdam for Alan's bucks party, getting whacked on magic mushrooms, losing Doug again and waking up with a llama in their room. And Mike Tyson will sing Tiptoe Through The Tulips.