He was born on 27 February 1933, fifteen minutes before his twin brother David, as eldest son of the 5th Marquess of Bute and of Eileen, Marchioness of Bute, herself the younger daughter of the 8th Earl of Granard. He was educated at Ampleforth College, and Trinity College, Cambridge, where he read history. From 1947 to 1956 he was styled Earl of Dumfries, and in 1956 succeeded his father as 6th Marquess of Bute. His full titles, with the dates of their creation, were: Lord Crichton (1488), Baronet (1627), Earl of Dumfries, Viscount of Air, Lord Crichton of Sanquhar and Cumnock (1633), Earl of Bute, Viscount Kingarth, Lord Mountstuart, Cumrae and Inchmarnock (1703), Baron Mountstuart of Wortley (1761), Baron Cardiff of Cardiff Castle (1776), Earl of Windsor and Viscount Mountjoy (1796). He was Hereditary Sheriff and Coroner of the County of Bute, Hereditary Keeper of Rothesay Castle, and patron of 9 livings, but being a Roman Catholic could not present. He was Lord-Lieutenant of Bute from 1967 to 1975, and of Argyll and Bute from 1990 until his death.