As I write, my cats and a visitor from the next street are hammering into their food, at nearly £5 a box. Once they only ate greens to make themselves vomit, but now they relish food labelled, ‘garden fresh’, containing carrots, pumpkin and pulses, plus ‘prebiotics to aid digestion’.

I watch them eat and wonder how cats have evolved so quickly from savage carnivores into something more like middle-class ladies getting their five a day.

Not that long ago, pets were fed scraps or, if they were lucky, Spratt’s Patent Food, which provided Puss and Fido with boiled horse flesh and beef blood, sold from barrows by street urchins. Tinned food arrived from the US in 1922. It made dog poop white, something that doesn’t seem to grace our pavements now. But the days of hearty, masculine-sounding pet foods like Chum and Chappie are over. Pet food today is about dietary virtue, advertised with words such as ‘whole’, ‘nature’ and ‘holistic’ — and it’s slowly becoming about ethical virtue, too. And then late last year, vegan cat food arrived in the UK.

American cats have eaten ethically for the past 20 years. The arrival here of meat-free pet food was inevitable, as the number of vegans in Britain has increased from 150,000 to 542,000 in just ten years. More than half are female and under 34. They also have spending power, which is why Pret a Manger and Wagamama have just introduced vegan food. Marks & Spencer, Sainsbury’s and Tesco have done the same. (Not one of those three have taken any interest in using sustainable palm oil in their Christmas produce, sticking to the old planet–destroying variety.) Even Greggs, as of last week, offers a vegan sausage roll.

As an animal lover but not a vegetarian, I was agnostic about vegan pet food until I heard a leader of the vegan ‘community’ on Radio 4. He was angry. There was that tell-tale high moral tone and those key words and phrases: ‘Narrative’, the story of his struggle against ruthless capitalist forces; ‘hot-house’, the future of the planet if a specific course of action isn’t taken right away; ‘tipping point’, the destruction that awaits if our cats fail to turn vegan.

Vegetarian identitarians (not a phrase to use with a mouthful of alfalfa), like trans-gender men, LGBTQI, black feminists, anarcho–primitivists, hunter-gatherers and Ulster loyalists, are mostly fuelled by anger and unresolved anxiety. Listening to the angry vegan leader, it seemed to me very unfair of him to offload his own psychological issues on to cats, who are actually ruthless, unrepentant carnivores.

Not eating meat is, of course, complex. Some vegans are driven by concerns about global warming, others by simple squeamishness. A lot of women say they dislike red meat and tend to be vaguer about this than about their problems with wheat and dairy, which for some reason they can’t digest. All pet owners these days — particularly cat owners — identify closely with their pets. There’s a trend in the US for referring to cats as ‘fur babies’. No wonder then that Lily’s Kitchen offers feline food which is grain-free, organic and hypoallergenic.

At the National Pet Show in Birmingham in November, there was a large display of vegan food and ‘ethical’ non-meat alternatives. The RSPCA was unimpressed; in fact it got quite snarly and pointed out that cats depend on taurine and arachidonic acid, found only in red meat. Without it, they can suffer bladder stones and blindness. The charity threatened that owners not feeding their cats meat could contravene the Animal Welfare Act 2006, and might soon be sampling prison food.

American cats have been forced into veganism for most of this century: they’re fed on kitty kefir, kombucha and kimchi. But the veganism is the last stage in the American de-catting of cats. Many are de-clawed, something illegal here, and kept indoors. They wait for their owners to return from work, then act like feline stress-relievers.

Happily, British cats are still — so far — free to shake off their owners’ issues. They shoot through the cat-flap and over the fence to gobble up mice, or get their dinner next door if necessary. They depend on humans, they’ll scoff their ‘garden fresh’, but they’ll never go hungry for the sake of an ideology. They’re too canny for that.