Key, he was educated at Dulwich College in London and commissioned onto the Unattached List of the British Army on 1 October 1914.
[1] He was wounded in Mesopotamia in 1918 and received the Military Cross, the citation for which reads: For conspicuous gallantry and devotion to duty near Shuraimiyah on 20th October, 1918.
Although exposed to heavy fire the company successfully reached its objective, where he moved about fearlessly in order to make his dispositions to the best advantage.
[1] After the First World War Key served in Afghanistan and, with the 3/11th Battalion, Sikh Regiment on the North West Frontier.
Attending the Staff College, Quetta, from 1931 to 1932, in 1935 he was promoted to lieutenant colonel and from 1936 he commanded the 2nd Battalion, 11th Sikh Regiment.