He was additionally Geddes–Harrower Professor of Greek Art and Archaeology at the University of Aberdeen from 1972 to 1973, and, in retirement, visitor to the Ashmolean Museum from 1979 to 1987.

[3] Haynes began his academic career as a scholar at the British School at Rome from 1936 to 1937: during this time he undertook research for his first book, Porta Argentariorum, which was published in 1939.

[2] In 1939, Haynes was invited to join the staff of the British Museum by Bernard Ashmole, the newly-appointed Keeper of Greek and Roman Antiquities.

[1] With the outbreak of the Second World War, he was involved in the preparing and packing of the British Museum's extensive collection for safe storage.

[2] It was layer revised and expanded to target a wider audience, and published as Antiquities of Tripolitania ten years later.

[1][5] Among the galleries created, was one built specifically for the Bassae Frieze with the same interior dimensions as the Temple of Apollo from which they originated.

[2] Haynes retired from the British Museum in 1976,[1] and was succeeded as Keeper of Greek and Roman Antiquities by Brian Cook.

[1] Following the Second World War and his marriage to Sybille, Haynes lived next to the British Museum at 89 Great Russell Street, London, and then at 24 Hereford Square, South Kensington.

[1][6] Haynes led an active retirement, dedicating time to academic research and published a number of works.