After telling Will that his film, Hancock, was "sick" and asking what the actor's own favourite role had been, one young fan blurted out 'you rock!' and got a little more than he probably could have dreamed of...
More top news
A lamp in the tower which houses Big Ben is to be switched off for the first time in more than 70 years.
Sir Bruce entertained audiences for more than seven decades.
Work in the tower will also pause over the bank holiday weekend.