ITV News Deputy Political Editor Chris Ship, who is at David Cameron's PM Direct event, wrote on Twitter:
Cameron got cheer & standing ovation BEFORE his talk here. Either they are all Tories or they really like the Budget http://t.co/4QPa0ThMBC
More top news
Wayne Rooney and his wife Coleen are expecting their fourth child, the couple have announced.
As the silence came to an end the crowd began to applaud and people shouted "I am not afraid!" in defiance of the attacks.
Italian Bruno Gulotta, 35, and Belgian mother Elke Vanbockrijck have been confirmed among the dead after a van mowed through crowds.