He became heir apparent to the earldom in 1815 on the death of his elder brother, Lord Hay, who was killed during the Waterloo Campaign.

[4] In 1839 he was promoted to Lord Steward of the Household on the decease of the Duke of Argyll, a post he held until the administration fell in 1841.

[7] Lord Erroll married Lady Elizabeth FitzClarence, the illegitimate daughter of King William IV and Dorothy Jordan, on 4 December 1820.

They were the parents of four children:[8] Lord Erroll died in London in April 1846, aged 45, and was succeeded by his eldest son, William.

Lord Erroll was the chief organiser of the Dublin Bay regatta held in Kingstown (now Dun Laoghaire) in 1828.