[3] Born in Alresford, Hampshire to Cyprian Robert Knollys (1868-1940), a land agent descended from a junior branch of the family of the Earl of Banbury and his wife Audrey (née Hill; 1871-1957), he was educated at Winchester College and Christ Church, Oxford.
Coombs was killed in a World War II air raid in Belfast in 1941, which led to the bereaved Knollys closing the gallery in 1944.
[7][8] In 1945, Knollys, Edward Sackville-West, 5th Baron Sackville and the music critic Desmond Shawe-Taylor jointly bought a Georgian rectory in Long Crichel, Dorset, where along with the gay activist and eye surgeon Patrick Trevor-Roper, literary critic Raymond Mortimer and James Lees-Milne, they established "what in effect was a male salon, entertaining at the weekends a galaxy of friends from the worlds of books and music".
[8][9][10] Milne recruited Knollys to join him at the National Trust during World War II, and over the next 15 years accompanied him on many of the trips to country houses recorded in his published volumes of diaries.
In 1965, Knollys inherited a large collection of artworks from Edward Sackville-West, which he added to and on his death in 1991, bequeathed to the Bulgarian emigre and picture framer Mattei Radev, a former lover of E.M. Forster.