The third instalment of his illuminating and waspish society diaries, Types and Shadows, follows his two bestselling diaries, Splendours and Miseries 1967-1987 and Scenes and Apparitions 1988- 2003. A N. Wilson reviewed the first volume of the diaries saying, "At every word a reputation dies". Strong has continued that tradition in successive volumes.

Types and Shadows, covering the period 2004 to 2015, takes its title from Thomas Aquinas: "Types and shadows have their ending, for the newer rite is here". In this third volume, Strong is entering the winter of his life.

The diaries open in January 2004. His wife, theatre, ballet and opera set designer, Julia Trevelyan Oman, had died three months earlier. They conclude with Strong celebrating his 80th birthday and receiving news of his forthcoming appointment to the Order of the Companion of Honour for services to the nation's culture.

Oman's death left him alone in the 23 rooms at Laskett, their Herefordshire country house, the gardens famously designed by Strong and Oman. The diaries recounts his failure over the next decade to persuade the National Trust, whom he compares to the Stasi, to take the gardens over.

While Strong rails against the ageing process and the banalities of the world around him as he perceives them, and regrets the loss of beloved friends, Types and Shadows provides a still-vibrant, entertaining window on Strong's life. This was a decade which included many lectures, dinners, travel, exhibition openings, television appearances, publications and a new prestigious ceremonial role as High Bailiff and Searcher of the Sanctuary at Westminster Abbey.

Strong refuses to acknowledge frailty, but, he admits, "At the assemblies of the ailing, everyone is getting older and older and more and more decrepit and unkempt". While he writes, "I don't want this diary to descend to the level of being a repetitious account of memorial services", there are numerous memorials, including the one for Billy Talon, Page of the Back Stair to the Queen Mother at Clarence House, a house "which ran on alcohol". Talon, we learn, died of sclerosis of the liver.

Strong believes that "we have no great leaders of this country bar the Queen". Other members of the royal family fare less well. The Duke of Edinburgh's "face and skin are pretty far gone", Camilla, Duchess of Cornwall, is likened to "the wife of a public school headmaster", while Prince Charles, who apparently always travels with two valets, wears "his hair scraped back, or rather what's left of it".

In 2005, his book, Coronation: A History of Kingship and the British Monarch is published. Strong believes that the next coronation, of Charles III, will have to be "more inclusive, to use that ghastly word". It won't, however, be able to replicate the coronation of Charles II, when 400 virgins paraded through the streets of Bath.

He attends a number of dinners at which the Queen and Prince Philip are present, including an intimate one at Lambeth Palace in which he finds "two glasses on the table already filled with red and white wine and food just put before you on a plate . . . I don't think that the Queen notices food very much".

At the wedding of Prince William and Katherine Middleton in 2011, he worries about "the lack of loos" in the Abbey. He writes, "the nave became like a cocktail party minus the drinks and canapes", so afterwards, he drops into a Pret a Manger shop for a sandwich. "The counter staff looked a trifle amazed, but, yes, I'd had a very good day."

Strong is a great defender of the English past. Now everything is "rapidly crumbling". He regrets that "political correctness had stood the world on its head", laments the drop in educational standards and that the music of Andrew Lloyd Webber has replaced Mozart at Buckingham Palace balls. He sees the Tony Blair government "as sunk in sleaze". Plus ca change with the current Johnson government.

Numerous, somewhat acidic pen portraits abound. Michael Portillo "is a charming, self-satisfied egotist, with coarse if engaging features"; gardening guru Diarmuid Gavin is seen as "oozing sex rather than any profound horticultural knowledge", while the new Queen Mary cruise ship is likened to "a vast block of council flats, dislodged and floating out to sea".

Strong has said that he sees his current diaries, "as the jottings of a self-employed writer observing a scene in which he is no longer a central figure". With a concluding section of 70 pages of biographical details of the "names" featured in the book, that may be too modest a claim.