Mercifully, Sir David's guide to etiquette is one that won't affect us lesser breeds
What should you wear if invited to go shooting game in Scotland? Should a host give a tour of his stately home before sitting guests down to dinner?
How much should one tip the servants after spending a weekend with friends in the country?
I don't know anyone who is much disturbed by these questions, but the world of toffs is filled with anxious sorts who turn to Sir David Tang for nervous guidance on social matters and his advice has become renowned.
Sir David is a wealthy and stylish Hong Kong businessman and philosopher who dispenses advice to the pampered clientele of the Financial Times and an unrivalled network of global celebrities. His book of advice, Rules for Modern Life, has been endorsed by Sir Michael Caine, Sir Mick Jagger, the Duke of Marlborough, Joanna Lumley, Naomi Campbell and Stephen Fry, among others.
Perhaps in eras of shifting values, there are always new rules of etiquette and someone has to set the standard. And it does lift the curtain on how the other half lives.
Consider the question of tipping the servants. "What is the appropriate amount of money to leave in a large country house in England - as a single woman I usually leave £10 per night in my room?" Sir David answers that, as the tenner will be shared between the butler, the cook and the housemaid, this is parsimonious. The tariff is £50.
Is it permissible, he is asked, to ask to examine the guest list before agreeing to attend a dinner party? And once arrived, is it rude to surreptitiously change the place names to your own advantage? And how does one cope with last-minute cancellations? "We Chinese have no qualms on insisting to see the guest list before we accept, which is sensible". But switching the placements is a no-no: a good host will have given close thought about who is next to whom and the success of the evening may depend on it.
As for cancellations, Sir David says he is always resigned to the fact "there will always be five or six people who cancel at the last minute, either because they are liars or half-liars". People who cancel frequently are known as "jackers", and Sir David receives anguished cries about guests who are "serial jackers". But his advice is: "Be relaxed about cancellations."
But gosh, the rich can be spoilt. How about this: "My husband and I hosted a small dinner party for a couple for whom we even changed the original date to suit. On the night they spent the entire time before dinner telling our guests they were double-booked and couldn't stay for the whole evening…" A problem which even afflicts the less rich is bringing a fine bottle of wine to a dinner party, which the host then squirrels away and instead serves you plonk. The only answer is that "the host is a prat". Though Sir David himself is a teetotaller.
How does a woman greet an old lover encountered in unexpected circumstances? Say: "To show how magnanimous I am, I am willing to forgive your stupidity and give you another chance". And immediately demand a night at the Ritz, a diamond from Graff and a house in town and in the country. Blunt, but perhaps ironic.
What do you do if your best friend marries "someone ghastly?" Sir David has "several friends who are married to ghastly spouses". It's easier if the friends are male, because a chap can drop the "ghastly" wives for all-male business lunches or poker games: trickier the other way about, because affairs may be suspected. And that's complicated.
What happens if a friend goes down in the world? "My wife and I asked an old friend to be godfather to our eldest child and he agreed. Since then, however, he's quit his job and has not worked for two years. He has generally become unreliable. We regret our decision and would like to choose someone else now. What should we do?" Forgotten, it seems, is the notion that a godparent is appointed to ensure the spiritual welfare of a child. It has now transmogrified into provider of expensive gifts. Sir David counsels: "Get someone richer and more dependable, and substitute your wayward friend by an honorary godparental appointment, in case the prodigal does limp back".
There are a few practical tips we lesser breeds might pick up. It's outdated to serve ladies first at dinner parties. Decanters are not necessary to let wine breathe - just uncork the bottle in advance. Neckties should never be stored rolled-up, but should be hung.
If you have to leave a gathering early, don't make a song and dance of it - just vanish with a swift farewell. If people don't return hospitality after three invitations, stop inviting them. A gentleman should wear shirts with cuff-links, but never, now, cravats. It's not naff to burn scented candles - Princess Diana always did it at Kensington Palace. And thank-you letters, whether electronic or by snail-mail, should begin with something more interesting than "thank-you".
He cites Barack Obama's model thank-you to the author Yann Martel: "Mr Martel, my daughter and I just finished reading Life of Pi together. Both of us agreed we prefer the story with animals. It is a lovely book - an elegant proof of God and the powers of storytelling. Thank you. Barack Obama". Yes, that is class.