He was the eldest son of Captain Francis Grant-Gordon RN and Mary, daughter of Sir Willoughby Aston, 5th Baronet of Risley, Derbyshire.

[4] He was appointed Assistant Adjutant General in Ireland in 1795 and in 1801 under Colonel William Henry Clinton commanded the 85th Regiment of Foot in Madeira following its capture.

[4] He was made Military Secretary to Prince Frederick, Duke of York and Albany, the Commander-in-Chief of the Forces in 1804, during which period he gave what Thomas Creevey regarded as "pompous, impudent evidence" to the House of Commons enquiry into the Mary Anne Clarke Affair.

Despite the veracity of this narration being questioned by many during this time, Gordon publicly proclaimed his faith in the truth of Adams' story, announcing that "if he proved an imposter, he will be the second only to Psalmanazar."

[11] On 15 October 1805, Gordon married Julia Lavinia, daughter of Richard Henry Alexander Bennet of Northcourt Manor, Shorwell, Isle of Wight.