Balfour was son of Sir Robert Arnot of Fernie, chamberlain of Fife.
Thereupon, by a letter from King James I, Arnot became Lord Balfour of Burleigh, the second holder of the title.
He was also constituted of the privy council ad vitam aut culpam by the parliament of Scotland 11 November 1641.
Montrose defeated him 12 September 1644 near Aberdeen, and again (with General Baillie) at Kilsyth, 15 August 1645.
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