John Simpson on protests in Turkey, China and Prague
14 June 2013 Last updated at 11:17 BST
The BBC's world affairs editor drew on his international reporting experience to look at how protests can work - and whether they change opinion.
John Simpson looked at governments using force on demonstrators in Turkey today, and China in the past, and said: "the best protest I ever saw was in in Prague", where protesters got their way without a window being broken.
Michael Portillo claimed Margaret Thatcher was brought down by his then-fellow Conservative MPs fearing the loss of their seats, and not the community charge - or poll tax - protests in Trafalgar Square.