Mason (Derrig), Sinéad (‘Jenny’) (1899–1991), civil servant, was born 2 March 1899 in Craigaroddan, Ards, Co. Down, eldest of eight children of Thomas Mason and Catherine Mason (née Merron). Educated at Ballyphilip national school, Ards, she moved to Dublin to live with her aunt Jane Mason and continued her education at the Holy Faith convent, Haddington Road, Dublin, and St Michael's Loreto convent, Navan, Co. Meath. Having worked briefly as a secretary with a firm in Baggot St., she was secretary to Éamon de Valera (qv) for a brief period in 1919 prior to his departure for the USA. From 1919 to 1922 she served as personal secretary to Michael Collins (qv), working long hours throughout the war of independence. Because of her close relationship with Collins, many of his friends and relatives felt that he might marry her. Opposed to the Anglo–Irish treaty, in 1922 after the death of Collins she took up a post in the Department of Local Government, resigning in 1928 on her marriage to Thomas Derrig (qv), Fianna Fáil TD and later minister for education. They lived at 58 Dartmouth Square and 33 Pembroke Road, Dublin, with their two daughters. She shared a number of interests with her husband, including reading, walking, theatre, and opera. She died 3 April 1991 in Dublin, where she lived the latter part of her life at 6 St Helen's Road, Booterstown. Before her death, she deposited in the NLI a copy of a journal kept by Michael Collins while he was in Sligo jail in 1918.
Liam C. Skinner, Politicians by accident (1946); Tim Pat Coogan, Michael Collins (1990); Íosold Ó Deirg, ‘ “Oh Lord, the unrest of soul”: the jail journal of Michael Collins’, Studia Hib., xxviii (1994), 734; information from Íosold Ní Deirg (daughter)