But — reverting to Fowles’s diary entry — surely honesty is the quality most essential in a diarist. It comes before all the others: a good prose style; a sense of humour; a memory for dialogue; an awareness of setting, with an eye for significant detail; a critical faculty with a tinge of malice; a skin too few and a willingness to make a fool of oneself. For diarists with one eye on posterity (and Lees-Milne surely had that) a further quality is needed: a serene assurance that you will be as interesting to other people as you are to yourself. Gore Vidal coined a phrase for the kind of man Lees-Milne was: an ‘objective narcissist’ — one who gazes at himself with fascination, but notices his flaws as well as his virtues.

Early in these diaries we get a taste of Lees-Milne’s acute observation, coupled with his entertaining literary style, in his account of a National Trust committee meeting in London.

Lord Zetland, the Trust’s chairman, is wry, starchy and pedagogic; Lord Esher, like a dormouse, small, hunched, quizzical, sharp and cynical; Ronnie Norman, the eternally handsome schoolboy, noisily loquacious until he finds the conclusion to an argument, when he stops like an unwound clock; Nigel Bond, dry, earthy, sound, unimaginative; Sir Edgar Bonham Carter, twisted by arthritis, fair, impartial, but too subdued to be heeded by the others; Mr Horne, the old, sweet-sour yet genial solicitor, who has sat in attendance ever since, as an articled clerk, he helped draft the constitution of the National Trust in 1895, now beyond his prime, and havering.

You have the feeling that these judgments, if on the waspish side, are probably fair.

Lees-Milne’s prose mastery enlivens the diaries throughout. He can be laconic:

At 8.20 I telephoned Q., who I knew would still be in bed. She answered the telephone. I said, ‘It’s me, Q.’ ‘Is it you, Terry?’ she said in a voice of unconcealed excitement. ‘No,’ I answered, and put the receiver down gently.

He can get ecstatically gushy, as when he meets Pope Pius XII in 1948, but even that afflatus is suddenly punctured by a wry observation at the end:

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