John Stuart, Lord Mountstuart and 1st Marquess of Bute (1744-1814) was the eldest son of the prime minister, John Stuart, 3rd Earl of Bute (1713-92) and Mary Stuart née Montagu. He was educated at Harrow School, Winchester College, and the University of Oxford before going on his Grand Tour in 1761-5 in the company of James Boswell. In 1766 he married Charlotte Jane, heiress and daughter of the second Viscount Windsor.

In the same year, he sat as MP for Bossiney and committed to a career in politics, although he was left frustrated by Lord North’s indifference towards him. He served as Lord Lieutenant of Glamorgan from 1772-93, and subsequently Lord Lieutenant of Bute from 1794-1814, he was sworn of the Privy Council in 1770, appointed auditor of the imprest in 1781 and took the post as Ambassador to Spain in 1795-6. His diplomatic services led to his creation as 1st Marquess of Bute in 1796.

In 1798, Stuart renounced diplomacy but failed to gain the position of Lord Steward, or receive the Garter. He became a fellow of the Society of Antiquaries in 1766 and of the Royal Society in 1799, as well as a trustee of the British Museum in 1800. He returned to politics after the death of his first wife in 1800, becoming a Councillor of State for the Prince of Wales. He remarried in the same year, to Frances Coutts, daughter of the banker, Thomas Coutts. He died in Geneva in 1814 and was buried in the Bute vault at Roath, Cardiff.

There has been a fortification on the site of Cardiff castle since the Roman period and it has been rebuilt and altered so much that the present building comprises an assortment of fabric from different periods, including Roman, Norman, Medieval, Georgian and Victorian, as well as the twentieth century. In 1776, John Stuart inherited Cardiff castle, following the death of his wife’s parents and he also inherited the title Baron Cardiff. The castle was in a ruinous state and Stuart endeavoured to transform the castle into a habitable and prominent building.

Stuart asked Robert Adam to make designs for additions to Cardiff castle. The surviving drawings, which date from 1777, include an elevation and three plans. The grand design proposed incorporating the existing castle into a much larger house comprising a three-winged structure in an angular arrangement, similar to the shape of a half-hexagon. The surviving plans helpfully show the layout of the existing castle in pink wash. The proposed additions do not appear to have been constructed, with Stuart choosing Henry Holland to design and make additions to the building instead in 1777-78, in collaboration with Capability Brown.

Literature:
A.T. Bolton, The Architecture of Robert and James Adam, Volume II, Index, 1922, pp. 6, 81; M. Girouard, ‘Cardiff Castle, Glamorganshire – I: The property of Cardiff City Corporation’, Country Life, April 6 1961, pp. 760-3; S. Parissien, 'Adam and Holland', Adam in context, Georgian Group Symposium, 1992, pp. 55-60; D. King, The Complete Works of Robert & James Adam and Unbuilt Adam, Volume 1, 2001, p. 390; Volume 2, 2001, p. 161; H. M. Colvin, A Biographical Dictionary of British Architects 1600-1840, 4th edition, 2008, p. 528; R. Thorne, ‘Stuart, John, first marquess of Bute (1744-1814)’, Oxford Dictionary of National Biography, online, 2008, [accessed 5 January 2024]

Louisa Catt, 2024