John Mason was a notable figure in the Oxford academic world and Librarian at Christ Church for a quarter of a century. Mason did not publish as much as might have been expected of a scholar of his calibre. But among several high-class articles on the Norman Conquest, at least one, on Roger of Montgomery and his sons (1963), has remained indispensable for understanding how the Norman Conquest worked on the ground and especially in the important border region of his native Shropshire.

Mason’s other publications included a history of Bridgnorth, and — in collaboration with E. G. W. Bill — Christ Church and Reform (1850-67), an important work examining the radical changes in 19th-century Oxford. In general Mason was not among the most ardent supporters of change; relatively few people brought up in Shropshire are. But in this case, change brought about the diminishing power of the canons of Christ Church and the rising power of the Students (as its Fellows are called), and he would hardly disapprove of that.

Mason became Librarian of Christ Church in 1962, a position that he held for the next 25 years. This put him in charge, though answerable to the college’s governing body, of one of the two greatest college libraries in Oxford and it was in this capacity that he made his most significant impact on Christ Church and on the university. Christ Church was at that time filled with eminent and powerful figures, but the mild Mason, besides showing intensity and devotion in the way he did the job, surprised many, on the rare occasions when he deemed a fight to be necessary, by his steel and his Machiavellian stratagems.

Born in Pembrokeshire, he was educated happily and successfully at Bridgnorth Grammar School, Shropshire, won a scholarship to Jesus College, Oxford, in 1937, and after war service took a first in history in 1948.

During the war he served first in the Manchester Regiment, and from 1942 to 1945 in the Indian Army, rising to the rank of major. He was adjutant at the Mechanical Transport Training Centre on the present-day borders of Pakistan and India, becoming also an interpreter of Urdu. He would later describe himself at this time as “a pink youth of 19 (though more like 23) who had the authority to sentence grown men to up to nine months in prison”. He felt that he had, during the war, a degree of responsibility that was never to be equalled again in his life.

From 1950 to 1957 Mason was research lecturer/Student at Christ Church, Oxford, concerned with the papers, then at the college, of the Victorian Prime Minister Lord Salisbury. In 1957 he was elected official Student of the college, and remained so until his retirement in 1987.

He was a first-rate college tutor. It was not his style to deal in inspiring baroque monologues, but he was a good listener and an exceptionally discriminating judge of undergraduate work. He was loyal to all his former pupils; and his loyalty and affection were reciprocated, as their celebration for him at his retirement lunch in 1987 showed. When one contemplated Mason, with his moon-shaped face and placid looks, it was very easy, but very dangerous, to let one’s guard slip. He could politely floor someone talking nonsense, or amusingly correct factual errors of his interlocutor. If anyone’s wit could be called mordant it was his. A friend told him that he had just become a member of Worcestershire County Cricket Club. “Have you ever actually met a Worcestershire supporter?” Mason asked innocently. The friend remembered just in time that Shropshire had no first-class cricket team and that Bridgnorth was quite close to Worcestershire. Far from using his wit to put people on the spot, however, as Curator (that is president) of the Christ Church Senior Common Room he helped over many years to put countless guests of the college at their ease.

In 1941 Mason was married to Iris Bache, who died in 1989. He is survived by his daughter, Gillian, from that marriage, He subsequently married Sally Hirst, who also survives him.

John Mason, academic and librarian, was born on June 9, 1920. He died on October 31, 2009, aged 89