Backstage with Justine Bieber
Bieber fever swept through London on Monday as Justin Bieber rocked up to switch on the Christmas lights at two of the city's biggest shopping centres.
Thousands of the teenager's fans camped out for hours for a chance to see their idol and their screams were deafening!
We sent Joe backstage to meet the Bieber, but there was only time for one killer question...
Watch Joe's report to find out what he asked and, more importantly, how Justin reacted!