BEFORE you ask, yes, this is the boy band Hanson. We’re talking the same three, sweet-faced siblings who had a global hit back in the 1990s with MMMBop when they should have been starting secondary school. The real surprise is not that Hanson are still making music — what else do you do when you’ve sold ten million albums by your early teens? — but that the brothers from Tulsa are about to be big all over again. Only this time, it’s with old-fashioned rock rather than chirpy teen pop.

In the States, Hanson’s latest album, Underneath, has altered their image and given the band a new lease of life. It’s packed with self-penned, self-produced catchy melodies, their trademark three-part harmonies and vocals that are more John Mayer or John Cougar Mellencamp than the Backstreet Boys. They may still be cute enough to attract screaming teenage girls, but these days a Hanson gig will also draw thirty- and forty-somethings with a soft spot for Springsteen.

Underneath isn’t released in Britain until February but, judging by the sold-out crowd on the London leg of their first UK tour for four years, their classic American rock won’t have trouble crossing the Atlantic. Perhaps to prove that they were never the pop puppets many had imagined, Hanson introduced their new material and played a few tracks from their slim back catalogue with a simple, acoustic show.

Zac, Taylor and Issac sat on stools at the front of the stage, playing guitar, piano, percussion and harmonica and occasionally singing a cappella. It was an eye-opening experience. New songs such as Strong Enough to Break and the forthcoming single Penny & Me had big, catchy choruses, clever lyrics and hooks that stuck in your head, while delicate ballads such as Underneath and Deeper managed to be sweet without ever sounding soppy.

The obligatory MMMBop appeared near the end of a 90-minute set, but other tracks from the band’s Grammy- nominated debut album, Middle of Nowhere (1997), reminded fans that Hanson were never a one-hit wonder. The ballad I Will Come to You and the country-rock song When You’re Gone had the girls in the audience singing along from the start, while Run Away Run got arms (and a few glowsticks) waving in the air.

It is still hard to believe but Hanson appear to have done the almost impossible jump — from teen poppers to credible rockers