Sykes will be especially remembered for his 1975 memoir, the biography of his friend Evelyn Waugh. While both had attended Oxford, but a few years remote from each other, Sykes and Waugh met after the success of "Vile Bodies", 1930. He introduced Waugh, as a matter of course, to Lady Diana Cooper. Waugh would create one of his great personalities drawn from her characteristics and ways, Julia Stitch, in Scoop, 1938. Sykes praised "Brideshead", Waugh's Catholic epic; the two were both Catholics, but with the notable difference—mentioned by Waugh's son Auberon when reviewing Sykes's book in the November 1975 issue of "Books and Bookmen" – that whereas Waugh converted to Roman Catholicism in his twenties, Sykes was a cradle Catholic. He however admitted to a dislike of the character of Julia Flyte, noting that nobody had yet identified a model for her in contemporary society. Sykes makes some interesting comparisons between scenes in Waugh's books and those of William M Thackeray - the fox hunting scene in a "Handful of Dust" is compared to that in "Barry Lyndon."