Considering the school holidays don't start for another month, the last day of June seems an odd time to release what will surely be the hit of the season, writes David Parkinson.

But Chicken Run is upon us and no amount of clucking by grown-ups forced to spend their weekends queuing is going to change the matter.

One thing is certain from the outset - Nick Park's proud run of Oscar victories is set to end. Too long to enter the animation category and simply not good enough to challenge for Best Picture, this parody of the POW movie has, nevertheless, opened in the States to stupendous reviews and rocketing box-office. But, while there's no denying the audacity of its scope, the ingenuity of its creation and the sheer exhilaration of a couple of set-pieces, Chicken Run rather bumps along before it finally gets airborne.

Down on Tweedy's farm, there's a stirring in the chicken coop. The prospect of laying eggs until she's selected for Sunday lunch seems an unprepossessing outlook for an ambitious hen like Ginger and so she determines to escape. The entire credits sequence shows her failed attempts - each of which results in her being dumped (River Kwai-like) in a coal bunker, where she's reduced to bouncing a sprout off the wall (Great Escape-like). You've got to know your POW films if you're going to get all the gags here. In addition to the aforementioned, you might like to look up Stalag 17 and The Colditz Story to be on the safe side.

Back on Tweedy's farm, a rooster called Rocky has fallen from the skies and convinced Ginger that he can teach the hens to fly over the gulag's perimeter fence. Cue scenes of exercising and calamitous flight training, during which Mrs T. has decided to abandon eggs and go into the chicken pie business. The need to escape is, thus, greater than ever, but Rocky has been somewhat economical with the truth . . . Reviewing kids' films is a thankless task. Younger audiences are so tolerant of even the most dismally drawn cant (eg A Monkey's Tale) that it's hard to be objective about something that does its job (ie keeping the little dears quiet for an hour or so) so efficiently.

It's to Chicken Run's credit that it can't be considered in the same light. The Wallace and Gromit films have taught us to expect more and had this lovingly crafted film been of a comparable length, you would be reading nothing but effusive praise.

But there are longueurs here and many of them revolve around Rocky 'the Lone Free Ranger'. Clearly the fact that he is voiced by Mel Gibson has much to do with this. If you've got one of the world's biggest movie stars on board, you have to keep him occupied to justify his fee. But Rocky isn't the principal character. He's Ginger's love interest (as it were) and does little to drive along the plot. Thus, his big scenes are all diversions, whether he's being pampered while the hens do PT or organising a dance to smooth a few ruffled feathers. Similarly, Mrs Tweedy (voiced by Miranda Richardson) lacks the terrifying presence of a Cruella De Vil, partly because more of her invective is directed towards her doltish husband than the hens. A good villain is essential to the success of a kidpic and Mrs T. simply isn't nasty or visible enough to cast a sufficiently sinister shadow. The final nitpick is the lack of individuality among the hens. It's easy to identify Ginger (Julia Sawalha) because of her green bobblehat and the kooky Babs (voiced by her AbFab co-star Jane Horrocks) because of her blue-rinsed comb. But the rest are so identikit that even Rocky sometimes gets lost amidst the crowd.

Anyway, quibbles over - now for some of that effusive praise.

The plasticine world of Nick Park remains as enchanting as ever. There's no knitting dog or criminous penguins here, but there is a rooster who can ride a tricycle and a cockerel who served in the RAF.