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
6th Parliament of Queen Elizabeth I as possible but finally signed the death warrant on 1 February 1587. Even then she belatedly attempted to call it back but by then Mary had been executed at Fotheringhay Castle on 8 February 1587. Once Parliament had resumed sitting, the debate ill-advisedly turned towards matters of religious reform led by the Puritans Anthony Cope and Peter Wentworth, both of whom were immediately committed to the Tower for several weeks for ignoring Elizabeth I's ecclesiastical prerogative. After being advised to treat Puritans and sectaries as equal to Jesuits in their ability to undermine the stability of both church and realm