Having successfully rebooted the world's most famous puppets two years ago, British director James Bobin follows up with a sequel that is a little less warm-hearted, but probably more fun.

Part of the Muppet appeal for adults is the self-referential humour, something which Bobin - whose experience includes Da Ali G Show - has heightened here, the film opening with a musical number that contains the cheerily high-risk observation that "everyone knows the sequel is not quite as good".

After their successful reunion in the last film, the question on the Muppets' lips is, what now? They've discarded a number of options, including Gonzo With The Wind and the Swedish Chef starring in a remake of The Seventh Seal, when into the song walks wannabe manager Dominic Badguy (Ricky Gervais) with the suggestion that they embark on a world tour.

With a name like that, of course, Badguy must have an ulterior motive - and lo, Kermit is replaced with his evil double, Constantine, "the world's most dangerous frog", recently escaped from a Siberian gulag and intent on stealing the British Crown Jewels. Meanwhile, Kermit is transferred to the prison, where his showman skills will prove his salvation.

As the Muppets' tour steers them towards London, and this becomes a caper movie, we're reminded yet again how adaptable and appealing these creations can be.

Gervais is fine in the principal human sidekick role, but the chief sources of comedy come courtesy of Tina Fey's alluring gulag guard, Nadya, and the human/Muppet team of detectives on the villains' trail, namely Ty Burrell (channelling a stream of gags at the expense of the French) and Sam Eagle. Game guest stars include James McAvoy, Christoph Waltz and Miss Piggy's role model, Celine Dion.