In view of the widespread disquiet about the calibre, indeed probity, of some of those recently admitted to the House of Lords, it is timely to recall the example of a man of distinction who turned down the honour that others judged he richly deserved.

The opportunity to do so comes with the publication of the fourth and final volume of the letters of the Oxford philosopher (and so much else) Sir Isaiah Berlin.

The appearance of Affirming: Letters 1975-1997 (Chatto & Windus, £40) brings an end to a 12-year labour of love by editors Henry Hardy and Mark Pottle, whose meticulous research is apparent in each of its 600-plus pages, especially in the copious footnotes.

The detail of these was commented upon amusingly by the President of Wolfson College, Prof Dame Hermione Lee, during a reception held there (Berlin having been its first president) last Friday.

She might have added, as I did in an aside to fellow guest Sir Hugo Brunner, that notes on such as Joseph Stalin, Adolf Hitler and William Shakespeare were perhaps not strictly necessary.

Hardy spoke on his and Pottle’s behalf of their satisfaction over a task now completed, paying tribute to Nicholas Hall, whose diligent research played a vital role in the project.

The three are seen in my photograph, above, with a copy of an uncompleted portrait of Berlin by Lucian Freud. The original picture is soon to be loaned by the family, a number of whom, including Lady Berlin’s son Peter Halban, were present.

I was pleased to find among the guests my pal Nigel Rees, the long-time presenter of Radio 4’s Quote... Unquote on which, with no conspicuous brilliance, I have twice appeared. Nigel’s skills had been put to use in verifying a number of the quotations dotted throughout the text.

Another mate was present in the shape of Nick Utechin, a valued contributor in the past to the arts pages of The Oxford Times. His mother Pat, who died in 2008, had been the devoted secretary to Sir Isaiah and, as such, the first to have ‘read’ the letters.

These will have included the one to Margaret Thatcher in the first year of her premiership (1979) declining her offer of a peerage.

He told her candidly: “I look upon a life peerage as conferring not only a title and certain privileges but also certain responsibilities which I do not feel capable of undertaking.”

Mention of honours reminds me that fascinating insights into the way the system operates are found in the book. Berlin was a member of the secret Maecenas Committee which made recommendations concerning deserving recipients to the government of the day.

In January 1984, for instance we find him writing to the Cabinet Secretary Robert Armstrong urging a knighthood for his friend Geoffrey Warnock, the Principal of Hertford, “now upstaged by the damehood of his wife Mary”.

He also advanced the cause of Oxford historian Richard Cobb – “eccentric, unsober, but brilliant, a unique specialist on France.” He added: “It would show real imagination to make him a knight.” Alas, he did not make the cut. Perhaps the ‘unsober’ did it.

As Hermione Lee noted, the letters – perhaps the last such collection in this digital age – necessarily contain many of commiseration to the spouses of deceased friends.

These are models of tact, of good taste, of saying the right thing. I could not help noticing, however, how Berlin laid it on a bit thick in describing so many as ‘his best friend’. An overdone superlative, I would suggest.

He also had a habit of telling the recipients of these letters, what they wanted to hear. Natasha Spender, for example, always notoriously determined to rewrite the homosexual early life of husband Sir Stephen, was reminded how he had been deemed “unsatisfactory” by friends Auden and Isherwood for not imitating their attitude to the gay life.

I must not complete this short appraisal without saying how wonderfully entertaining these letters are, the gossipy ones – and there are many – especially.

It’s hilarious to find him putting the boot into the vain AL Rowse, for instance, and laying into another foe, Hannah Arendt.