He was closely involved with the lending of a copy of Magna Carta for the 1976 United States Bicentennial celebrations, and in succeeding years helped arrange the loans of several medieval manuscripts for the first time in half a millennium.

[1][5] Upon the December 1960 resignation of Julian Brown, a co-author of the paper who left for the chair of palaeography at King's College London, Turner assumed responsibility for the museum's collection of illustrated manuscripts.

[7] In 1971, Turner helped secure the Anderson Pontifical for the museum's collection, after it was discovered in the stables of Brodie Castle the previous year and placed for sale at Sotheby's.

[20] In the former role Turner helped oversee three major exhibitions: The Christian Orient in 1978, The Benedictines in Britain in 1980, and, with Janet Backhouse and Leslie Webster,[21] The Golden Age of Anglo-Saxon Art in 1984.

[24] In the process he enjoyed interacting with the Foreign and Commonwealth Office—and poring over abstruse indemnity arrangements—leading to the loan of a copy of Magna Carta to Washington, D.C. for the 1976 United States Bicentennial celebrations.

[24] The copy, the oldest of the four surviving, spent a year in the United States Capitol, where it was viewed by dignitaries including Queen Elizabeth II and Lord Elwyn-Jones.

[24] The following year, he helped lend the Gospels of Tsar Ivan Alexander to Sofia, Bulgaria, where it received national publicity; it had last been in the country in the fourteenth century.

[29] Learning that the son of a commuting acquaintance was interested in Anglo-Saxon literature, Turner invited the two to the library to handle the Beowulf manuscripts,[29] but among colleagues he had "a not undeserved reputation for being difficult and could chill the blood of the more timid".

[30] The unexpected death of his mother in 1966–1967, and his father's subsequent move into a nursing home, precipitated what Backhouse termed a "radical change" in Turner's life.

[1] Various studies were also published in his memory,[33][34] including "The Text of the Benedictional of St Æthelwold", a paper begun by Turner and finished by Andrew Prescott, then of the British Library.

[25] With the work "almost ignored previously", one reviewer wrote, Turner's facsimile was "stunning visually and always interesting";[37] another described a "brilliant introduction" that focused on history rather than art criticism.