A group of rats is called a mischief, and Cartoon de Salvo is one of the most mischievous companies around - a group of entertaining tricksters whose last show, The Sunflower Plot, was a whimsical delight. There has always been something childlike about this company, and they belong very much in the oral storytelling tradition of the fairytale where simplicity, ribaldry, the ordinary and the extraordinary, the best and worst of human nature all collide. So this combination of rodents and theatre, which updates the 14th-century story of mass child abduction to the 1960s, was a tasty prospect that should have given family audiences something delicious to gnaw upon this Christmas. Alas, even rats might want to look elsewhere for real sustenance.
The story of the Pied Piper is not very substantial. You get the impression that Cartoon de Salvo probably realised that early on, but instead of creating a tight little show of 75 minutes or so, they have gone for the full two-and-a-half-hour blow-out. The first rat doesn't make an appearance until almost 30 minutes in. You keep longing for them to ditch the padding, and get down and really tell the story.
There are some interesting ideas floating around: the updating is very clever, giving the story a contemporary accessibility, and Dennis Herdman's Ratcatcher has just the right mix of hippy-ish jester and sinister outsider. I also liked the way that the town's outward espousal of Christian values is totally at odds with the townsfolk's elevation of shopping into a religion. When the children finally climb Koppelberg Hill and disappear into the mountain, the production transcends itself; there is an extraordinary grace as each child stares into the light, as if they are seeing either the face of God or their deepest heart's desire.
The production also cleverly incorporates music - not just with a cheerful on-stage band, but also in the motif of a town that loses its children and then punishes itself by banning music, until the arrival of some carol-singers a generation later makes them rethink.
But good though these things are, they are spread too thin. There is something wrong when you leave the theatre feeling that the actors had a better time than the audience.
· Until January 14. Box office: 020-7223 2223.