William FitzWilliam (Lord Deputy) William FitzWilliam (Lord Deputy) Sir William FitzWilliam (1526–1599) was an English Lord Justice of Ireland and afterwards Lord Deputy of Ireland. In 1587, as Governor of Fotheringhay Castle, he supervised the execution of the death sentence on Mary, Queen of Scots. He was the Member of Parliament for Peterborough and represented County Carlow in the Irish House of Commons. He lived at Gainspark, Essex, and Milton Hall. FitzWilliam was born at Milton Hall, Northamptonshire, the eldest son of Sir William (d. 1576) and grandson of William Fitzwilliam, Sheriff of London, who had been treasurer and chamberlain to Cardinal Wolsey and
Mary, Queen of Scots of Lennox, who were Scottish aristocrats as well as English landowners, had sent him to France ostensibly to extend their condolences while hoping for a potential match between their son and Mary. Both Mary and Darnley were grandchildren of Margaret Tudor, sister of Henry VIII of England, and patrilineal descendants of the High Stewards of Scotland. Darnley shared a more recent Stewart lineage with the Hamilton family as a descendant of Mary Stewart, Countess of Arran, a daughter of James II of Scotland. They next met on Saturday 17 February 1565 at Wemyss Castle in Scotland, after which Mary fell