First World War Keith John Jeffery MRIA (11 January 1952 – 12 February 2016) was a Northern Irish historian specialising in modern British, British Imperial, and Irish history.

In 2005, he was commissioned by the British Secret Intelligence Service (MI6) to write an authorised history for the organisation's centenary, covering its founding in 1909 up through to 1949.

[6] A related study, The Defence of the Realm: The Authorized History of MI5 by Christopher Andrew was published in 2009.

[7][8] His 1916: A Global History, published in 2015, looked at how twelve events from different arenas of war, including the Irish rebellion, reverberated around the world.

[1][2] Jeffery died from cancer at Royal Victoria Hospital, Belfast, on 12 February 2016, at the age of 64.