[3] He was appointed Lieutenant Governor of Nevis in April 1761[5] (and so was briefly responsible for the juveniles Alexander Hamilton and Frances Herbert Woolward 1761–1831) was promoted to colonel[6] on 19 February 1762[4] and granted local rank as a major-general, commanding a cavalry brigade in the campaign of 1762.
[3] Johnston was appointed Lieutenant-Governor of Minorca in 1763,[7] promoted major-general in April 1770,[8] and made colonel of the 9th Regiment of Dragoons on 2 January 1771.
He transferred as colonel to the 1st Irish Horse on 27 April 1775[citation needed][11] and was promoted lieutenant-general in September 1777.
[3] On 5 May 1763, he married Lady Henrietta West, daughter of Lord De La Warr, leaving issue; his widow died in 1817.
[1] General Johnston died at Hampton 13 September 1797 in his 77th year and was buried in Westminster Abbey on 21 December 1797.