Subtitled An Enquiry into the Identifiable Characteristics of the English Aristocracy, this is an anthology of writings published more than fifty years ago. It all seems rather quaint to us now, but for some years the concept of U and non-U speech patterns spread rapidly from London to provide conversational pabulum at the dinner-tables of English-speaking Paris and New York.
It all started with a paper written by Professor Alan Ross of Birmingham University and printed in Neuphilologische Mitteilungen in Helsinki in 1954. The professor pointed out that it is solely by their language that the upper classes nowadays are distinguished, since "they are neither cleaner, richer, or better-educated than anybody else". He invented the useful formula: U (for upper class) speaker versus non-U speaker, giving examples of each.
Then one of the Mitford sisters (The Hon. Nancy, not the unrepentant fascist Diana, who married Oswald Mosley, or Unity, who shot herself for love of Hitler, or the communist Decca) wrote an article in Encounter about Ross's piece, which was followed by 'Strix' with Posh Lingo in the Spectator and attacked by Evelyn Waugh (a more sophisticated kind of snob) in Encounter. Christopher Sykes joined in with a piece called What U-future and finally John Betjeman wrote a poem satirising the whole U/non-U idea.
All this must have led many social climbers to worry about the words they used but of course it was all nonsense, though good fun. Anyway, aping your betters in this way wouldn't get you anywhere. It had to come naturally, you had to be born to it. If you needed to think about the words you used then you were irredeemably non-U.
[My copy of Noblesse Oblige is the Penguin paperback. Some booksellers offer "slightly battered" copies of this at £51. Mine is not battered but the cover falls off and the pages are very yellow, so I probably wouldn't get more than £30 for it; it cost me 2/6d.]