Having sold a whopping 73 million albums, there seemed little point in Backstreet Boys, the American boy band who make Westlife look like Babyshambles, reuniting. But having lain dormant since 2000's Black & Blue, they returned this year with a reasonable album, Never Gone, to find a diminished but still-viable market.

This, though, is an act in terminal, neglectful decline. Their choreography was sloppy, their harmonies under-utilised and their patter feeble: Nick Carter introducing Just Want You To Know with "does anyone here know what 'sphincter' means?" was neither big nor clever.

With the stirring exception of Incomplete, their music - from Shape Of My Heart (heart-shaped, I'd wager) to Don't Play With My Heart - was one-paced, vapid, anodyne gloop. This much the rather subdued audience knew and revelled in.

Less forgivable was the show's cheapness. Once Backstreet Boys used to fly above the crowd, now there were just two weedy explosions and chief vocalist Brian Littrell's grandfather-style pale blue jumper.

In fact, for all the strutting of Alexander "AJ" McLean (fresh from rehab and who briefly favoured us with a vest, tie and tam-o'-shanter ensemble), the quintet looked uninterested. Hence, perhaps, several long breaks for momentum-sapping video interludes.

The tubby, heavily perspiring Carter gave every indication of having spent his time since splitting with Paris Hilton and his drunk-driving arrest living on a diet comprised exclusively of pies, while Kevin Richardson, 33, and Howard Dorough contributed only lumpy dancing and the occasional harmony. Too lazy by half.