Born John Casey, in Dublin, O’Casey had a strong interest in the Irish nationalist cause. He joined the Gaelic League in 1906 and learned the Irish language. At this time, he Gaelicised his name from John Casey to Seán Ó Cathasaigh. He also learned to play the Uilleann pipes and was a founder and secretary of the St. Laurence O’Toole Pipe Band. He joined the Irish Republican Brotherhood, and became involved in the Irish Transport and General Workers Union, which had been established by Jim Larkin to represent the interests of the unskilled labourers who inhabited the Dublin tenements. He participated in the Dublin Lock-out, but was blackballed and could not find steady work for some time.

In March 1914 he became General Secretary of Larkin’s Irish Citizen Army, which would soon be run by James Connolly. On 24 July 1914 he resigned from the ICA, after his proposal to deny dual membership to both the ICA and the Irish Volunteers was rejected.

In 1917, his friend Thomas Ashe died in a hunger strike and it inspired him to write. He wrote two laments: one in verse and a longer one in prose.

Much of his writing is about the slums and poverty of Dublin which by any standards was appalling in the early twentieth century. The Abbey Theatre produced his first play ‘The Shadow of a Gunman’ in 1923 and the following year ‘Juno and the Paycock’. His production of ‘The Plough and the Stars’ resulted in riots by Abbey patrons who thought the play denigrated Irish heroes.

Image by Wolfgang Suschitzky, bromide print, 1955