Seán Murphy joined the IRB in 1901, and quickly became centre of the club to which he belonged, which met in the Foresters’ Hall in Parnell Square. He joined the Volunteers in 1913. He was involved in arranging for Eamon de Valera to meet Thomas McDonagh on Holy Thursday, 1916, apparently to be sworn in as a member of the IRB.

He missed the start of the Rising due to being in Bray on business, and joined the Jacob’s garrison on Monday evening. After the surrender, Slater describes talking to Sean McDermott in Richmond Barracks. McDermott said: “The cause is lost if some of us are not shot”. Slater was sent to Knutsford Jail, and thence to Frongoch internment camp, from which he was released at Christmas, 1916.