There are two kinds of great stag nights in the world: those you wont ever forget and those that push the boat out so far you cant even remember what happened. The Hangover is about the latter, delivering 100 minutes of steady raucous laughter about a bachelor party gone very very wrong.

Determined to give their friend a good send off, Phil (Cooper) and Stu (Helms) take their best friend Doug (Bartha) to Vegas for his stag night accompanied by Dougs strange almost-brother-in-law Alan (Galifianakis). But when they wake up in their devastated hotel room the next morning, they have no recollection of what happened the previous evening and no idea what happened to Doug, who has mysteriously vanished.

What follows is a hilarious comedy mystery, as the three remaining members track down clues to find out what the heck happened the previous night. They play three male archetypes, but its a testament to writers Lucas and Scott, that they remain sympathetic no matter what irresponsible behaviour they get up to. Bradley Cooper gets to plumb the depths of male arrogance and does so brilliantly, Ed Helms plays a hen-pecked husband let off the leash to a tee and Zack Galifianakis loner loser type is played more as a 30 year old child rather than the obvious stereotypical oddball.

Its a tightly-woven and well-plotted script that will keep you guessing till the end. The laughs come thick and fast, particularly from Galifianakis, who brilliantly manages to walk a very thin line between tastelessness and comedy. Its not always successful but when it is, its laugh out loud funny. A lot of out of the ordinary things that happen to the group (babies, tigers, Mike Tyson), but its grounded with a plausibility that makes it just about believable – outrageous certainly but not ridiculous.

It sounds odd to praise the cinematography in a comedy film, but Las Vegas looks so incredible that youll want to jet over there yourself and it provides a realistically glitzy backdrop to the trios raucous antics.

In a world currently dominated by the over-rated escapades of Judd Apatow and Co., its nice to see a film that breathes new life into what is essentially an old concept. In 2000, Todd Phillips directed Road Trip, which was a funny if sometimes puerile movie. Now, nine years on, its as if those very characters have grown up and the directors sensibilities along with them. The result is a clever, well-written and above all funny movie and probably the best mainstream comedy of the summer.

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