When I was starting out as a standup, I worked nights in an orange juice factory. I got £3.50 an hour and as much orange juice as I could lick off my two hands. The amount of orange concentrate we added to the raw drink at the initial stages determined whether it was bound for expensive upmarket outlets or to cut-price corner-shop providers. It was a quick and easy process to alter the product according to demand.

Illustration: David Foldvari

The worst part of the job was hosing out the maggots that hatched from fruit fly eggs laid beneath the conveyor belts, and periodically jammed up the gears with their crushed bodies. Sometimes I stayed on the shop floor after hours, pleading with the insects to find a safer place to deposit their unborn. But, like my readers, they didn't listen to me, preferring to repeat the same errors endlessly, as do you.

David Cameron visited the Pinewood film factory recently and told the UK film industry it should "try to support more commercially viable pictures", laying his eggs beneath the production line. But can "commerciality" be added to a piece of art as simply as adding extra concentrate to orange juice? David's friend, the Tory peer Julian Fellowes, who made scattershot implausibility universally addictive with the arbitrarily scripted second series of Downton Abbey, endorsed a review of UK film that said public money should be spent on films "that more people want to see". British film-makers, represented as usual by Ken Loach, joined a queue of soon-to-be-silenced dissenters seeing all Tory policies as ideologically driven mind-control programmes disguised as economic rationalism.

But perhaps David is right. Maybe it is actually possible to manufacture a hit. Admittedly, no one saw the smash new movie The Artist, a silent black-and-white comedy with no name stars, coming; Stan Lee's publisher advised him against writing Spider-Man because "people don't like spiders"; David's unwilling faves the Smiths were written off in their first NME live review as "Go-Betweens copyists"; the BBC, which eventually took credit for The Office, was still asking how to bury it when it was first broadcast; and Life's Too Short, a supposed dead cert from The Office's creatively and commercially successful team, was a critical and ratings disaster. But maybe David is party to a formula for popularity, despite the fact that no art of any real value, including all Hollywood films of the past 30 years, has ever been made by pursuing one. Good artists do what they believe in and don't merely court public approval. In these respects they are the opposite of politicians. Zing!

Today's Conservatives rationalise everything by financial value. When I was still young, Mrs Thatcher toured St Hilda's College, Oxford, and asked a girl what she studied. "Norse literature," she said. "What a luxury," replied the prime minister, anticipating the current government's suspicion of humanities, but not anticipating the subsequent global financial value of the Lord of the Rings franchise. Fed by Tolkien's study of Norse myth, the trilogy bled out of The Hobbit, which he originally wrote for a minority audience no bigger than that comprising his own bedtime children.

(Tolkien is, however, rumoured to have charged his offspring all their pocket money to hear the end of the tale, having already got them hooked. This "first hit's for free" technique he learned dealing heroin to CS Lewis, who only began the Narnia chronicles in order to have a reason to meet his supplier every week in the Eagle and Child pub. Anyone who has ever tangoed with Sister Brown Eye will recognise immediately the safe warm feeling of falling into a wardrobe full of fur coats. And then having tea with a man with goat's legs.)

So, is Tolkien's own luxurious study of Norse retroactively financially validated by box office and sales of Gandalf action figures with the face of Sir Ian McKellen, or was it worth doing anyway because a civilised country values knowledge in and of itself? And would these McKellen-faced toys fall foul of Thatcher's Clause 28 legislation anyway, by virtue of promoting homosexuality, or at least a magical homosexual, to impressionable children?

Because the press tire of stories quickly, David's next prescriptive encounter with disgruntled creatives was largely ignored. On Friday David was winched bodily up the Faraway Tree to Slumberland, for a photo-op with the Traum Gnaums, who weave our dreams in their mouths from gossamer and hope, before travelling to Earth to spit them into the brains of sleeping people. David intended to convince the Gnaums to take a more practical approach to the business of dreams. But their ruler, Prince Guabo, was not impressed.

"Cameron got off on the wrong foot immediately," he confided. "His opening gambit was, 'Now, which one of you was it gave Ed Miliband the dream of being leader of the Labour party?' It was the kind of route-one gag that would probably get a round of applause off the claques of city boy Top Gear wankstains he usually addresses, but dream-weaving is a creative vocation, not a business. A lot of the Traum Gnaums are liberal arts types so it fell a bit flat."

David suggested that, instead of dreaming of being dancers or spacemen or clowns, children should be encouraged to dream of, for example, studying economics while being financed by corporate sponsors with a view towards structured apprenticeships within approved educational partner companies. And he said that the meaning of dreams should be clearer, in order to give them a greater mass appeal. Gnaum Guabo disagreed. "For us, that's the beauty of dreams. They're mysterious and opaque, collisions of symbols and stories all swooshing around. They stay with you, but it's not clear why. And often their meaning isn't apparent until months or years later. Cameron's telling us dreams should match people's desires in an obvious and more immediately profitable way. I think I can speak for the Traum Gnaums when I say that isn't why any of us got into dream weaving."

Last week I went out for my daily Calippo with comedian Richard Herring, who I used to write with in the last century. I told him about this piece. He said: "It sounds like the sort of clanking satire we used to grind out for Radio 4's Week Ending in the 1980s. Take some existing fantasy or mythological trope and overlay it with contemporary policy. Is the Observer buying it?" "Yes," I admitted, sheepishly. "Then well done," he spat through his frozen flavoured ice. "It's a commercial idea. And so it is good."

Stewart Lee is currently appearing in Carpet Remnant World at the Leicester Square theatre, London, and touring nationally from February. stewartlee.co.uk