QUB professor was one of the world's top military historians
Professor Keith Jeffery, who has died aged 64, was a distinguished military historian who wrote the early history of MI6.
He was Professor of British History at Queen's University and only retired on January 21.
Queen's extended its sympathy to his wife Sally, sons Ben and Alex and the wider family circle.
It added: "Keith was rightly known as one of the world's most distinguished historians, and as someone who made an immense contribution to the annals of British and Irish history.
"His appetite for accuracy, along with his talent for storytelling, ensured that a rich vein of enthusiasm for his work extends far beyond academia. As a result, thousands have been enriched and enlightened by his work.
"Those lucky to have known Keith, be it as a friend, colleague or absorbing lecturer, will miss him, and remember him with great fondness.
"His publications were often credited as fascinating, endlessly interesting and never to be superseded. On his death, we apply those sentiments to him."
Keith John Jeffery was educated in Ireland and the USA, and at St John's College, Cambridge, where he was awarded the Prince Consort Prize and Seeley Medal.
In 2005 he joined the staff of Queen's, after teaching at the Ulster Polytechnic and the University of Ulster for over two decades.
His expertise in military history was recognised globally and he held a number of posts overseas. From 1997-98 he was a Visiting Fellow at the Australian National University and Australian Defence Academy, New South Wales.
In 1998 he was Lees Knowles Lecturer in Military Science at Trinity College, Cambridge, and from 2003-04 Parnell Fellow in Irish Studies at Magdalene College, Cambridge. In 2004 he was also a Visiting Research Fellow at Deakin University, Melbourne.
Professor Jeffery was greatly in demand internationally as a lecturer. In 2003 he gave the Phillimore Lecture at the British Library, the Stout Lecture at Victoria University, Wellington in 2004, and the fourth annual Centre for Intelligence and International Security Studies Lecture at Aberystwyth in 2006.
The next year he was awarded the Templer Medal from the Society for Army Historical Research for his biography of Sir Henry Wilson, judged the best book of the year on British military history. In 2009, he was elected a Member of the Royal Irish Academy.
From 2005 he was seconded to the Cabinet Office to write the official history of MI6, and in 2010 he published MI6: The History of the Secret Intelligence Service (SIS), which covered the years 1909-49.
He later returned to his work on the First World War period, and only last year he published his book 1916: A Global History.