Born in Killaloo, Derry he became involved in the civil rights movement and was President of the Derry Citizens’ Action Committee, 1968-69. He was elected to Stormont as an Independent member for Mid-Derry in 1969 and co-founded the Social Democratic and Labour Party (SDLP) in 1970.
On 30 January 1972, he organised a protest march in Derry during which fourteen unarmed men were shot dead by soldiers. This became known as Bloody Sunday. He was elected to the Northern Ireland Assembly for Mid-Ulster in 1973 and was Minister of Community Relations in 1974, but left active politics in 1983.