William Grant was the second surviving son of Sir
Francis Grant by his first wife, Jean Meldrum, daughter of the Rev. William Meldrum of Meldrum, Aberdeenshire. He was admitted an advocate on 24 February 1722, and on 13 May 1731 was appointed
Procurator to the General Assembly of the Church of Scotland, and
Principal Clerk to the General Assembly. In 1736, Grant wrote a pamphlet
Remarks on the State of the Church of Scotland with respect to Patronages, and with reference to a Bill now depending before Parliament, On 20 June 1737 he succeeded
Charles Erskine of Tinwald as
Solicitor General, and on 28 August in the following year was constituted one of the commissioners for improving the fisheries and manufactures of Scotland. Upon the retirement of
Robert Craigie, Grant was appointed
Lord Advocate on 26 February 1746, and on 20 May following the assembly held that the lord advocate could not act as procurator and clerk, and that consequently these offices were vacated. At a by-election in February 1747, Grant was returned to parliament as member for the
Elgin Burghs, and on 1 April 1747 was "added to the gentlemen who are appointed to prepare and bring in a bill for taking away and abolishing the heretable jurisdictions in … Scotland". Grant took part in the debate on the second reading of the bill, and is said by
Horace Walpole to have spoken "excessively well for it". This important measure of Scottish reform was subsequently carried through both houses and passed, as well as another bill, which had been introduced by the lord advocate and the English law officers, for the abolition of ward holding. At the general election in July 1747 Grant was again returned for the Elgin burghs, and in April 1749 supported the grant to the city of Glasgow for the losses sustained during the rebellion in a vigorous speech. On 24 February 1752 he introduced a bill for annexing the forfeited estates in Scotland to the crown inalienably, which after some opposition became law. He was for the third time returned for the Elgin burghs at the general election in May 1754, but vacated his seat on his appointment as an
ordinary lord of
session and a
Lord of Justiciary in the place of
Patrick Grant, Lord Elchies. He took his seat on the bench on 14 November 1754, and assumed the title of Lord Prestongrange. In the following year he was appointed one of the commissioners for the annexed estates. Grant died at
Bath on 23 May 1764, aged 62 or 63, and was buried on 7 June following in the aisle of Prestonpans Church, Haddingtonshire, where a monument in the churchyard was erected to his memory. ==Works==