On the death of Robert McQueen, Lord Braxfield, Fergusson was made an ordinary lord of session, and took his seat on the bench as "Lord Hermand" on 11 July 1799. He was also appointed a lord justiciary on 4 August 1808, in the place of Sir William Nairne of Dunsinnam.[3] He resigned both these offices in 1826.
Fergusson was both eccentric and a heavy drinker. An etching of Hermand by John Kay is in the first volume of 'Original Portraits' (No. 156). His portrait also appears along with those of the other judges in the 'Last Sitting of the Old Court of Session, 11 July 1808' (vol. ii. No. 300).[4]
He died at the family estate of Hermand House east of West Calder and west of Edinburgh, on 9 August 1827. Hermand House and its estate still survive.
Family
Fergusson married Graham (sic), daughter of William McDowall of Garthland, who survived him by several years. They had no children.