[2] After graduating from the Royal Military College, Sandhurst, Kell was commissioned into the South Staffordshire Regiment on 10 October 1894,[3] and promoted to lieutenant on 15 December 1896.

He could speak German, Italian, French and Polish with equal facility, and after serving and studying in China and Russia, he learned their respective languages too.

He was promoted to the rank of captain on 24 September 1901,[6] while still seconded in China where he served as a Railway Staff Officer (for which he was mentioned in despatches).

[9] Rising public fears in Great Britain of German espionage precipitated the creation of a new government intelligence agency.

[9] Following the outbreak of war in 1914, Kell was restored to active duty as a GSO 2,[13] and was promoted to the temporary rank of lieutenant-colonel on 5 September.

[31] Kell is depicted as an ally of a secret society of bodyguards attached to the radical women's suffrage movement in the graphic novel trilogy Suffrajitsu: Mrs. Pankhurst's Amazons (2015).

[33] In Bill Aitken's novel Blackest of Lies, Kell is involved in the concealment of Lord Kitchener's fictional death at the hands of the Irish Republican Brotherhood.