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 legal counsel and that as a foreign anointed queen she had never been an English subject and thus could not be convicted of treason. Mary was convicted on 25 October and sentenced to death with only one commissioner, Lord Zouche, expressing any form of dissent. Nevertheless, Elizabeth hesitated to order her execution, even in the face of pressure from the English Parliament to carry out the sentence. She was concerned that the killing of a queen set a discreditable precedent and was fearful of the consequences especially if, in retaliation, Mary's son, James, formed an alliance with the Catholic powers