Superfans of the royal wedding have been camping for days on the Mall to secure their spot for the nuptials.
But they weren't expecting that their dedication would give them a chance to meet Prince William.
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The future King stunned thousands of well-wishers when he turned up for an impromptu walkabout on the Mall.
Seeing the crowds swelling, he decided to personally go and chat to them.
There were huge cheers – and quite a few tears of happiness – when the Prince arrived with his brother Prince Harry from Clarence House at about 8.30pm.
A sea of hands reached out and camera phones were raised in their hundreds as William moved along the crowds to thank people personally for their support.
He joked with the crowd "don't worry, I'll be OK," though he did confess that his biggest concern was that "I won't get my lines right."
Dressed casually in a pale shirt, black jumper and chinos, the Prince paid special attention to the children in the crowds.
Harry - the best man – kept his distance as to not draw attention away from the man of the moment.