Seán MacDiarmada, member of the Provisional Government of the Irish Republic. He was the principal IRB organiser and has been described as ‘the mainspring’ of the Rising.

MacDiarmada had a leading role in planning the 1916 Rising. Well aware that most previous Irish revolutionary movements had been bedevilled with spies and informers, he was obsessively secretive in his planning, excluding most of his fellow IRB men from knowledge of the conspiracy, which was eventually to contribute to the confusion surrounding the outbreak of the Rising.

MacDiarmada spent the Rising in the General Post Office with most of the other members of the Provisional Government. Although he had no formal military rank, he was acknowledged by the garrison as one of the commanders due to his membership of the Provisional Government and his role in the IRB. He was tried by court-martial and executed by firing squad in Kilmainham Jail on 12 May, he and James Connolly being the last of the leaders to be executed.