. Steuart was the second son of Colonel William Stewart (d.1691),
adjutant to
James Graham, 1st Marquess of Montrose at the
Battle of Philiphaugh, by his wife Barbara, the granddaughter of
James Stewart, Earl of Arran, the
Lord Chancellor of Scotland. His paternal grandfather, William Stewart of
Burray, lived at Mains,
Wigtownshire, and was the elder brother of
Alexander Stewart, 1st Earl of Galloway. Steuart himself was a first cousin of
John Sinclair, 8th Earl of Caithness, and a nephew of Lt.-Col. Sir Archibald Stewart (d.1689), the first
Baronet of Burray. His father had been granted lands in Ireland by
King Charles II in lieu of arrears of pay due to him as a
Cavalier officer during the
English Civil War, and it was there that William Steuart grew up. He joined the
English Army and became a
captain with the
1st Foot Guards before his promotion by
William III of Orange to
lieutenant-colonel of the 16th Foot. He was subsequently promoted to
colonel of the
9th Regiment following the
Glorious Revolution. Before Stewart took command, the regiment had taken part in aborted attempt to relieve the
besieged city of Derry under another Colonel
John Cunningham who was dismissed by King William for his failure. Stewart's regiment was re-embarked as part of General
Percy Kirke's second relief force for Derry. He served with distinction for the remainder of the
Williamite War in Ireland against the
Jacobite Irish Army. At the first
Siege of Limerick (1690) he was badly wounded in the right hand, permanently disabling him was wounded again at
Limerick and
Athlone. He was promoted to
brigadier-general in 1694 and then to
major-general in 1696. On Christmas Eve, 1700, he fought a duel with Colonel Bellew. Within two yards of his opponent, Steuart, with his left hand, shot Bellew through the hat. In return Bellew threw away his pistol saying that he did not desire to kill Steuart. By 1703 he was promoted to
lieutenant-general. In 1711, in the absence of the
Duke of Ormonde,
Queen Anne appointed him
commander-in-chief of her forces in Ireland. The same year he was made a full general and
Privy Councillor.
George I later removed him from his colonelcy of the 9th Foot, suspecting him of 'favouring the Chevalier'. He lived at
Hanover Square, London and was a member of Parliament for
County Waterford from 1703 to 1715. He owned considerable amounts of land in Ireland that after his death was distributed between his nephews and nieces, the children of his deceased brother, James. General Steuart died 4 June 1726, and is buried with his first wife in the vault of the
Duke of Buckingham at
Westminster Abbey. In his will he left £5,000 to endow a school for the poor boys of his parish,
St. George's, in London. He also donated the land on which
St George's, Hanover Square was built, laying the first stone in 1721. The auctioneer Christopher Cock sold the house and its contents in Hanover Square, on 14 April 1730. ==Family==