[1][2] He was the third son of 1st Viscount Elibank of Selkirkshire and his wife Blanche Alice née Scott of Portsea, Portsmouth, Hampshire.
[1][2] The family moved to Dresden in Germany in 1886, and he received his early education in the city, before attending Blairbridge School in Scotland.
[1] In 1898 he left the United Kingdom to begin a career as a colonial administrator when he became private secretary to George Le Hunte, Lieutenant-Governor of British New Guinea.
Two years later he was created a resident magistrate in the Western Division of the colony, and in 1901 was appointed acting commandant of the Armed Native Constabulary.
[1][2] A staunch supporter of Ulster Unionism, he broke with the coalition government led by David Lloyd George in February 1922 over its Irish policy, and did not defend his seat at the general election in November of that year.
In 1925 Gideon commissioned a portrait of Ermine by Philip de László which hung in their London house in Pelham Place.
A tireless worker on committees and social gatherings, much of which is recorded in the biography of her close friend Lady Dorothy Dalrymple.
After Gideon's death some six months later at the Belmond Mount Nelson Hotel in Cape Town South Africa she returned to England and took residency in the Lansdowne Club.