Have you written your thank-you letters yet? Mother’s words continue to dog most of us for life. They hover like a black cloud over the season of festive giving and partying. We all vaguely expect a letter of thanks, but find them a crashing bore to write. Thanks sent immediately are thanks redoubled, we were told. “No duty is more urgent than that of returning thanks” – Saint Ambrose.

The thank-you letter is a last bastion in what Mary Killen (The Spectator’s witty social problem-solver) has called an “epidemic of discourtesy”. The postal strike this year did its best to kill off the personal letter, but for my generation, whose youth was punctuated with billets doux and penfriendship, a letter remains a tangible, portable, idiosyncratic and expressive form of communication. Princess Diana – who would now have been 46 – was probably one of the last of those well-brought up gels, or “chicks”, who never failed to write enthusiastic thanks in her girlishly round but emphatic hand.

The next generation seems content to live in a letter-free zone, as texting and e-mailing suffice. According to a recent survey, a third of under35s have never sent a personal letter to a loved one in their lives. The arrival of post, for them, means bank statements, parking fines, junk mail, offers to take on debt. Envelope-licking, stamp-sticking and walking to a letter-box are effortful. (My offspring would leave letters unstamped, the address often incomplete, on the hall table, trusting a parent to finish the task.)

I sought the view of the etiquette expert Drusilla Beyfus. As she says, after any enjoyable event or welcome gift, a letter writes itself; the chore is composing thanks for something you didn’t particularly like. Typewritten thanks are fine – and easier to read – as long as you top and tail in writing, and add a hand-written coda. “And you can get away with an e-mail, between friends,” she allows, “despite the impersonal typeface and the discouraging “Please consider the environment before printing this e-mail”. But if you value your own writing skills, a letter – using a proper pen, not a ballpoint – is much preferred and it can be kept.” I am in two minds: like most journalists I write faster on screen, but I know that people get more pleasure from a proper letter by post.

Emily Post’s 1922 guide to social politesse devotes 12 pages to sample thankyou letters, mostly brides expressing surprise and ecstatic gratitude for even humdrum wedding presents. Nearly a century later they remain useful: “The tea cloth is perfectly exquisite! I appreciate your lovely gift more than I can say, both for its own sake and for your kindness in making it for me.” “I have always wanted a piece of jade, but I have never imagined one quite so beautiful as the one you sent us . . .” “Really you are too generous . . . but I thank you with all my heart.”

Older relations in particular despair today over the thankless young. But we all sympathise with godchildren and nieces as we read their infant platitudes, imagining the adult standing over them until the task is done. Katharine Whitehorn, author of Social Survival, believes we must all “go with the currency”, accept the changing times, and be content with phone calls, “which are better than no thanks at all”. I once persuaded my tiny son to write his laborious thanks and gave him a minimal formula: “Thank you very much for the (blank). I like it very much.” His aunt reported back that his card to her read, “Thank you very much for the £10. I like it very much.”

“But now the etiquette has hotted up,” Whitehorn says. “In my day you didn’t have to thank people just for a meal. Today, not only must you not arrive at dinner empty-handed, but you’re expected to write afterwards.” Quite so. “Lovely evening, delicious supper, excellent company!” is all very well, on a postcard, but this formula makes it too blandly interchangeable with dozens of others, so if you read it years later, you would be quite unable to recall what was the delicious fare you lovingly prepared. Was it rabbit stew, tarte tatin, squab pie? “Wonderful sorrel soup – where do you find your sorrel?” is more helpful.

Someone once wrote to us “So long and thanks for all the fish” which sounded odd, until we realised it was the title of Volume 4 of The Hitch-Hiker’s Guide to the Galaxy. Also, it’s hard to recall who were those “excellent” companions unless you keep a fancy hostess book. Much better to write a more specific message, naming names ( I must disguise with initials here.) “I loved meeting S” is nice, but “I wish I could have liked A. W. just a little, but he is so frightening” is much more interesting. “Didn’t warm to C either,” added a guest of mine, with originality, “but I would always want her on my side.” “I loved the way R plumped up your cushions and rearranged your flowers,” said an observant guest, and “When your Von Trapp family burst into song it was just like My Best Friend’s Wedding” reminds us of a slightly embarrassing soirée. “I loved being among old friends – I’ve lost any desire to meet new people” is a comment that flatters the hostess’s careful selection of guests.

You can always find something kind to say about your hostess’s garb/ charming table/glowing fire/splendid wine. After all, letters are intended to bring pleasure, and should gratify the busy hostess’s feat of organising the occasion. Also, offer some instance of WHY you had a good time, what made it memorable. Give your hosts (who may miss the best conversations of the evening while they dart off to the kitchen) some inkling of what they could not be part of.

In letters you can verge on the libellous, assuming you have trustworthy friends: “G was wonderfully indiscreet about F getting drunk in the green room.” “I always adore seeing B, tho’ I did find the new wife hard work.” More snide comments (“Aren’t G’s teeth terrible?”) are strictly for very old friends in a morning-after phone-call, Virginia Ironside says, never written down for posterity to haunt you.

“What a party!”or “What a weekend!” is like “What a performance!” to an actor backstage after the show, a useful portmanteau. So is “From the moment I stepped through the door I knew I was in for a good time – and how right I was!” But appreciating the detail – a charade, a good story, a rude guest (“JH seems to have become a latterday Jeremy Paxman”) enlivens the thanks. Even small catastrophes can be found amusing and made light of. Following a crash of plates from the kitchen, or smoke billowing out from a burnt offering, or a sudden tearful departure, or some enthralling in vino veritas disclosure, your letter may refer to the evening’s drama, but must add something like “as we drove home we agreed, if only all parties could be as entertaining.” Or use Noël Coward’s line from the chorus of I’ve Been to a Marvellous Party: “I couldn’t have liked it more.” Few responses to invitations are as instantly negative as Philip Larkin’s Vers de Société: My wife and I have asked a crowd of craps/ To come and waste their time and ours: perhaps/ You’d care to join us?/ In a pig’s arse, friend.

And few thank-you letters are as candid as Cole Porter’s gritted-teeth song: “Thank you so much, Mrs Louseborough-Goodby . . . for that infinite weekend with you . . .

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