Conservationist of the built environment. Succeeded his father John Crichton-Stuart (1847 - 1900), the 3rd Marquess of Bute. Crichton-Stuart inherited his father's interest in conservation, being responsible for the preservation of Robert Adam's work on the north side of Edinburgh's Charlotte Square. He rationalised the family estates selling much of their land and properties in South Wales and setting in motion the gifting of Cardiff Castle to the people of that City.