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
Fotheringhay Castle claim to the castle through David and was to form part of the dowry of Joan, Henry III's sister who was to marry the Scottish king. On 3 December 1219 Marshal finally gave Fotheringhay Castle to the English king. According to the Barnwell chronicler, Hubert de Burgh, 1st Earl of Kent, was given custody of Fotheringhay Castle in 1221 when he married the King of Scotland's sister. The castle had yet been transferred to the control of the King of Scotland and was still effectively an English castle held under Henry III. William II de Forz, 3rd Earl of Albemarle,