★★☆☆☆

It is a brilliantly simple idea. Take a teenaged J-pop trio, introduce them to the joys of heavy metal, and you have a way of combining the cuteness of Japanese kawaii culture, such as perky choreographed dance routines, matching outfits and bright smiles, with the fantastical imagery, pummelling riffs and unrelenting darkness of metal. It is the kind of thing that festival audiences love, not least because Babymetal do it all with a perfectionist but tongue-in-cheek charm. Over an entire concert, however, the limitations of the Babymetal schtick were laid bare.

The three young, female members of the band, in outfits that fell somewhere between Xena, Warrior Princess and the Sugar Plum Fairy, let out painful shrieks for Gimme Chocolate! while backing musicians