John Simpson on protests in Turkey, China and Prague

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.

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