Born Sinéad Mason in Craigaroddan, Ards,
County Down on 2 March 1899. She was the eldest of eight children of Thomas and Catherine Mason (née Merron). She attended Ballyphilip national school, Ards, moving to Dublin to live with her aunt Jane Mason and attend Holy Faith convent, Haddington Road, Dublin, and later St Michael's Loreto convent, Navan,
County Meath. She worked briefly in a firm on Baggot Street as a secretary, going on to work briefly as
Éamon de Valera's secretary before his tour of the United States in 1919. Derrig was close to Collins, leading to many of his relatives and friends believing that he might marry her. After the death of Collins in 1922, she took up a post in the Department of Local Government. She resigned her post in 1928 when she married
Thomas Derrig. The Derrig's lived with their two daughters, Úna and Íosold, at 58 Dartmouth Square and 33 Pembroke Road, Dublin. Derrig refused to give interviews regarding her work with Collins later in life. She died at her home 6 St Helen's Road, Booterstown on 3 April 1991. Shortly before her death, she gifted a copy of a journal by Collins from his time spent in Sligo jail in 1918 to the
National Library of Ireland. == References ==