Exit through the gift shop. Pick up a postcard, a magnet, a novelty eggcup in the shape of Queen Elizabeth I. Treat yourself to a replica Rosetta Stone, a Babylonian bookend, a build-your-own Leonardo trebuchet. Tuck your little one up at night with a cuddly Anubis the dog.

Nicholas Coleridge, chairman of the Victoria & Albert Museum, has put the tat among the pigeons by telling the Cheltenham Literature Festival that the V&A shop is more successful than the BM’s. ‘The British Museum shop,’ said Coleridge at an event to promote his memoir The Glossy Years (available in all good gift shops), ‘increasingly sells teddy bears wearing police helmets, while the V&A shop sells the most beautiful jewellery and incredibly lovely William Morris drying up towels — very, very popular things.’ Last year, the tills of the V&A’s main shop rang up £7.3 million worth of calendars, Christmas cards and Frida Kahlo floral headdresses.

Meanwhile, the British Museum is a grand bazaar of Viking chess sets, plastic gladiator helmets and Horse Guards’ bearskin booties. Keep those tiny tootsies toasty. The exquisites at the V&A may scoff, but aged seven I’d have sacrificed my own mummy for an Egyptian hieroglyphs stencil set.

Besides, South Kensington isn’t without sin. For every Morris tea towel there’s a pair of Mary Quant lurex tights and a ‘Three Graces’ iron-on patch showing the comely bottoms of three G-stringed ladies. Which is stretching Morris’s ‘Have nothing in your house that you do not know to be useful, or believe to be beautiful’ beyond its usual limits.

When it comes to museum gift shops, they’re all as naff as each other. The National Gallery shop is awash with parakeet salt and pepper shakers, cockatoo carafes, toucan necklaces, spitting snake bottle openers, aubergine dipping bowls and other quasi-Tahitian titbits to tempt you on your way out of the Gauguin Portraits show. Single postcards? There were none. Only mixed packs of 16 for £8.50. When you’re only after a sunflower still-life, it’s a lot to spend for 15 duffs.

Postcards are a public good. For the student who can’t afford a catalogue, for the school-trip child with pocket money to burn, for the pensioner already stretching for a ticket, a 65p postcard keeps a canvas bright in the mind for years after an exhibition. I still have a propped-up postcard of the Arab Hall at Leighton House bought 20 years ago. That sense of wonder — Aladdin in west London! — comes back to me every time I catch the card in the corner of my eye.

This time of year is peak bauble. Forget snowflakes and tinsel — for a truly stylish tree this Christmas you want a tin alligator waving a pom-pom (£12.95, National Gallery), a glittery glass Brussels sprout (£6.50, Royal Academy) and Tippoo’s Tiger in tufted felt (£17.50, V&A). Because nothing says ‘Season’s greetings’ like a man being mauled by a tiger. (Obviously I want one.)

Let’s not be too tasteful. I’m as susceptible as the next shopper to ‘heel-arious’ hosiery inspired by ‘David Sock-knee’ and ‘Footloose Lautrec’. I am seriously considering buying my civil servant husband a portcullis-pattern Fair Isle jumper from the House of Commons shop. I covet a Salvador Dalí rubber duck — a crackers quacker — complete with curling moustache and melting wristwatch.

When did the duck thing happen? Every castle, every monument, every stately home now has its flotilla of costumed mallards. Greek duck, Roman duck, Samurai duck, Sphinx duck, Suffragette duck, Henry VIII duck, Winston Churchill duck giving the peace sign and smoking a cigar…

There is a serious point here. If we are not going to let our galleries take money from the naughty Sacklers (opioids) or from nasty BP (oil), if we are fundamentally opposed to admission fees (boo!) and budget cuts (hiss!), then we are going to have to accept a more mercenary museum culture. When the National Portrait Gallery called a press conference earlier this year to unveil its development plans, I winced at the ground floor becoming a palatial retail space. Enter via the gift shop. Exit via the gift shop. Never leave the gift shop! Now, as sponsors are censured and spurned without so much as a ‘so long and thanks for all the dosh’, I grudgingly admire the NPG’s foresight and wonder if it might have gone further still. Why not offer the ground floor to Apple or Nike? Prime location. Fine fixtures and fittings. Quick squint at a Holbein with every iPad.

Art isn’t free. Curators, restorers, archivists, lecturers, guards and, yes, the girl behind the gift-shop counter all have to be paid. And that’s before you start on lighting, heating, insurance, education, outreach, acquisitions, exhibitions, special staircase installations and dusting the Parthenon marbles. Without corporate sponsorship, it’s going to take a lot of teddy bears to keep the BM and co in business.

The quackers, incidentally, have missed a trick. There is as yet no ruffed and goateed Sir Anthony van Duck.