The elder son of Kenneth Mackay, 3rd Earl of Inchcape and his wife Aline Thorn Pease, he has a younger brother, James Jonathan Thorn Mackay (born 1947), and both were educated at Eton College.
Inchcape was then commissioned into the 9th/12th Royal Lancers, after training at the Mons Officer Cadet School.
[1] His sister was Lady Lucinda Louise Mackay, 13 December 1941 – 25 November 2024[2][3] He is a descendant of Cornelius Vanderbilt.
[1] He was Master of the Worshipful Company of Grocers for 1993-1994 and is a member of the Oriental Club.
[1] His heir, Viscount Glenapp, is married to Rebecca Jackson of Cottisford, Northamptonshire.