And so, Ladies and gents, the Cornetto trilogy finally comes to an end. It's been six long years since the last instalment – 2007's Hot Fuzz – hit our screens; during which time Simon Pegg has been busying himself hobnobbing in the US with two Star Trek films, supporting Tom Cruise in Mission Impossible: Ghost Protocol, among other projects.

But the gang of Pegg, Nick Frost and director Edgar Wright have finally gotten around to completing the trilogy they began with 2004's Shaun of the Dead, that sees them tackle not only a hardcore pub crawl, but saving the Earth to boot.

For many, seeing the back of their school days is a major relief and not one they would want to dwell on. Not so for Gary King (Pegg); for him, his school days were the best days of his life, so much so that, it's fair to say, he's yet to grow up. All his mates at the time – Oliver (Martin Freeman), Peter (Eddie Marsan), Steven (Paddy Considine) and best friend Andrew (Frost) – have moved on, but not so Gary.

Twenty years after leaving school, Gary decides to get the gang back together again, to return back to Newton Haven for some unfinished business; to finally complete the holy grail of the golden mile: a pub crawl consisting of twelve pubs in one night.

Although initially reluctant, they all eventually agree. They soon discover that much has changed in Newton Haven, and not for the good. The pubs that once had character, have now been homogenised by the dominance of the chain pub. Not only that, there's something odd about the towns folk. Really odd. After a few more pubs, and several more beers, they realise that finishing the golden mile this time around may once again prove difficult, but for far more deadlier reasons this time around.

And we're off in what is the inaugural event of beer-drinking in the Olympics.

There's no denying that when the triumvirate of talent that is Pegg, Frost and Wright get together, there's an eager expectation that laughs will be aplenty. The problem with creating this unofficial trilogy however (the Cornetto tag pays a comic homage to Krzysztof Kieslowski's Three Colours trilogy, by means of coned ice cream treat, available in three different flavours) is that the hope is for each incarnation to be funnier than the last. And sadly this one isn't.

In order to make this film different to Shaun of the Dead (which is difficult as the premise is almost identical, just swap zombies for robots), Wright devotes at least half of the film to his reunion story; this allows Pegg, Frost and the rest of the crew to go through their familiar shtick, with the kind of sharp-edged banter Pegg and Frost have become synonymous with over the years.

On the one hand, it would have been interesting to have pushed this idea throughout the entire film, and just concentrate on the reunion theme. Pegg and Frost have proven they have more range than just comedy, and certainly with the likes of Freeman, Marsan and Considine on board, there was the ability to add a more dramatic edge to proceedings.

Unfortunately the robot invasion spoils things somewhat. For what could have been a quick and smart homage to The Invasion of the Body Snatchers (the original, naturally), ends up dragging its heels and dishing up nothing new. They pretty much ticked this box with Shaun so this is very much tired ground being covered here.

It also feels like Pegg is carrying the entire film, which he appears to occasionally struggle with. Considine and Marsan are undoubtedly talented actors, but comedy is clearly not their strong suit.

Despite some energetic performances, the last film in this comic trilogy resembles a pint that has been hugged by a light weight for several rounds – it initially goes down a treat, but the longer it's left to its own devices, the more noticeably flat it becomes.

So on this performance, Pegg, Frost and Wright have literally had one too many and, in hindsight, should probably have called time after Hot Fuzz.