They're known worldwide by millions of fans, and it was only this week that it was revealed One Direction have sold 12 million records in just a year.

But the boys aren't letting that slight detail get to their heads.

In fact they remain particularly down to earth given their star power as two fifths of the band turned up to a London shopping centre today to hold an impromptu gig.

Surprise! One Direction's Niall Horan and Liam Payne held an impromptu gig at Westfield shopping centre in west Lond...