The most famous of the Montrose Grahams, James Graham, 1st Marquess of Montrose, may have been born at Mugdock Castle in 1612. During the Bishops' Wars, a prelude to the Wars of the Three Kingdoms, Montrose briefly supported the Covenanters. He was imprisoned in Edinburgh in 1641 for intrigues against Archibald Campbell, 1st Marquess of Argyll, who was to become his arch-enemy. While Montrose was in prison, Lord Sinclair sacked Mugdock. Montrose returned there, however, until 1644 when he began his Royalist revolt, becoming the King's commander in Scotland. Mugdock was sacked again that year. Following the defeat of Charles I, Montrose was executed in 1650, and the lands were forfeited to the Marquess of Argyll. In 1661 Argyll too was executed, and Mugdock was returned to the Grahams, who restored the castle over a two-year period, building a mansion within the old castle walls. In 1682 the Grahams bought Buchanan Auld House near Drymen, a dwelling more fitting the title of "Marquess", though the family's official seat was kept at Mugdock Castle for a some time.