It is a book in which the ‘Igor’ alluded to, often and intimately, is Igor Stravinsky, in which ‘Willy’ is W. Somerset Maugham, ‘Charles’ is Charles Laughton, ‘Rex’ is Rex Harrison and ‘Vanessa’ is Vanessa Redgrave. Of course, we know at once the identities of ‘Gore’, ‘Tennessee’, ‘Truman’, ‘Wystan’ and ‘Aldous’, Gore Vidal, Tennessee Williams, Truman Capote, W. H. Auden and Aldous Huxley having been gifted with first names peculiar to them as well as enormous talent as writers. (Is it coincidence that all but the last should have been gay too? Guess so.) ‘Mick’ will not be identified with certainty until linked — as he still was at this time — with ‘Marianne’.

Mick Jagger and Marianne Faithfull represent the junior end of celebrity as it is depicted by Christopher Isherwood in The Sixties (Chatto & Windus, £30). This is the second volume of diaries by the writer and covers the period (as the book’s sub-title tells us rather unnecessarily, as I do now, too) the years 1960-1969.

Few iconic figures of the time are missing from its 750-plus pages, Isherwood and partner Don Bachardy, themselves being at the centre of the gilded social scene focused on Hollywood. Though the publicity sent out with the book refers to “wicked gossip”, the revelations supplied by Isherwood seem rarely if ever to have been offered with spiteful intent. Instead, he supplies a frank and dispassionate account of the colourful life going on around him. Once again — to use a metaphor that will for ever be associated with him — he is a camera.

This is not to say his judgment cannot be sharp. The most famous show-biz couple of the day, for instance, are dismissed with the words: “Richard and Liz Burton are completely corrupt; they think only of money.”

The novelist Rosamond Lehmann is described as “looking like a delicious suet dumpling covered in powder”. He adds: “She is such a cow.”

For someone destined to live to be 81, Isherwood seems unnecessarily worried about his health: reports on his activities, progress on his work and occasional hiccups in his relationship with Bachardy are punctuated with frequent hypochondriac-like observations about various parts of his body. On September 4, 1963, for instance, he complains: “I feel utterly exhausted, these days, and my throat is bad again.” But he had cause to feel intimations of mortality that day, reporting: “Today came the news of Louis Macneice’s death. I really hardly knew him, but he is the first of the Old Guard to fall. At 55.”

His hardly knowing Macneice struck me as odd; one had always assumed that the team we think of as ‘thirties writers’ — ‘Macspaunday’, as Roy Campbell called the best-known of them — were constantly together.

Isherwood certainly saw much of Auden. In the midst of his poetry tour of America in March 1963 the poet called on his friend and “he was an awful nuisance and stank up the place with smoke and had us drinking pints”.

Four years later he was back again during another tour. “Wystan seems to be drinking heavily (as well he may),” Isherwood reports, “but not drastically. We sent him off with a bottle of gin and a bottle of dry vermouth. He has to have his martinis.”

This will not surprise anyone lucky enough to have seen Alan Bennett’s The Habit of Art in which Auden is seen slugging back jugs of the stuff in between assignations with rent boys in his rooms at Christ Church.

Speaking of recent theatre successes, I was pleased to see Isherwood leaping to the defence of Clifford Odets whose The Country Girl, with Martin Shaw, is proving a big hit in the West End. On his death in 1963, both Time and Newsweek had joked: “Odets, where is thy sting?”

Isherwood complained to the editors: “An important American playwright deserves more than a perfunctory dismissal with a tastelessly exhumed pun.” Well said!