Most historians agree that if the start of the Troubles can be traced to one time and place, it is the civil rights march on Duke Street in Londonderry on the 5th October 1968. The demonstration had been banned by the government and when it went ahead police turned water cannon on the protestors and beat them with batons. Footage was beamed around the world – and in the space of a few hours life in Northern Ireland changed utterly.To mark its 50th anniversary, Enda McClafferty hears eye-witness accounts from people who were on the march, those who were opposed, and those who remember conditions and the atmosphere in Derry in the weeks beforehand.