‘Rightly is they called pigs,’ says a farmworker in Aldous Huxley’s Crome Yellow as he watches porkers grunt and squelch. Pía Spry-Marqués has no time for such nominative determinism. ‘Pigs,’ she points out, ‘are in fact quite clean animals.’ Wallowing in mud isn’t nostalgie de la boue, merely the only way of keeping cool if no shade or fresh water is available.

God disagrees with her. ‘The swine, though he divide the hoof, and be cloven-footed, yet he cheweth not the cud; he is unclean to you,’ he tells Moses and Aaron in Leviticus. While most Muslims and Jews still go along with this (as do Rastafarians, much to the dismay of pork-loving Snoop Dogg when he converted a few years ago), Roman Catholics defy the edict so insatiably (except on Fridays in Lent) that they may well be the world champion pig-guzzlers. The average Spaniard’s annual consumption is twice ours: 51.6kg (114lb), equivalent to 516 trays of sliced chorizo for every Spanish woman, man and child.

Growing up in Madrid, Pía Spry-Marqués ate pork galore. But what if she had also watched Peppa Pig? She writes:

A Spanish friend of mine,’ she writes, ‘recently told me how her niece, on finding out that chorizo is made from pork, decided she no longer wanted to eat it because she didn’t want to hurt Peppa or anyone from the family.

That set Spry-Marqués thinking about how little we know of the animals whose flesh we devour so greedily — and prompted her to write a scholarly but quirky history, the most cherishable work of pig-lit since Augustus Whiffle’s The Care of the Pig. From an 18,000-year-old wild boar’s tooth to a recipe for swine testicles with garlic, nothing piggy is alien to her.

Sows are on heat for only a couple of days in each oestrous cycle, she writes: ‘Boars, as you can imagine, are always up for it.’ Whereas stallions ejaculate an average of 70ml (2.4fl oz) at a time, boars produce more than triple that: 250ml (8.45fl oz). Almost half a pint! Getting so much semen into a sow is a slow business — ‘so much so that boars have been observed to fall asleep half way through the 15 minutes or so it takes them to ejaculate.’

As proof that ‘pig-headed’ should be a compliment she cites an experiment in which month-old piglets had to understand what a mirror was in order to locate their swill. ‘The mean time that it took those seven piggies to figure it out and find the food was 23 seconds!’ she exults, adding that this behaviour is ‘slightly more advanced than that of three-year-old humans’.

Pigs, she believes, are our ‘most resourceful and, dare I say it, closest friends’. I know what she means, having befriended one myself. Perdita turned up as a little stray piglet in 1993 and soon took over most of our garden as she swelled to the size of a sofa. How long, we asked the vet, do pigs live? ‘Hard to say,’ he replied. ‘Not many die of old age.’ Ten years passed before she turned up her trotters, and we mourn her still.

Must each man kill the thing he loves? The question haunts both these books. Having relocated from England to a bucolic life in la France profonde, Jacqueline Yallop and her husband decide to become more bucolic still by acquiring a couple of weaners and fattening them up for slaughter. Fearful of succumbing to cuteness, she won’t give them pet names: they are simply Big Pig and Little Pig. ‘How can the name “big” or “little” inspire affection?’

This seems disingenuous from someone living in a land whose most famous term of endearment is mon petit chou — and especially from someone whose prose tends to the lyrical. Sure enough, she feels an instant flutter of kinship and is soon cooing maternally over the fluffy fringe on their brows, the squat soft snouts, the knobbly knees. At feeding time the pigs splash their noses through the grain, ‘bringing them up white and floury, like old-fashioned Sherbet Dabs’.

Yallop and her husband insist that when the time comes, ‘we will kill them ourselves and we will do it here, at home’. She has no idea what this entails, and her background reading is none too encouraging. ‘To kill a hog nicely is so much of a profession,’ William Cobbett writes in Cottage Economy (1828), ‘that it is better to pay a shilling for having it done, than to stab and hack and tear the carcass about.’

Meanwhile, inevitably, she becomes ever more smitten. When British friends visit, ‘the pigs perform for them, nuzzling hands, chuntering greetings’. Everyone wants to tickle Little Pig on the belly, feed Big Pig a slice of melon. ‘I’m not sure anyone believes we’re really going to kill them.’

Will she or won’t she? Yallop teases readers with this recurring cliffhanger rather too often as the months go by:

Big Pig and Little Pig are supposed to die at my hand…I’d better face up to it…The moment is nearly upon me… I’ll have to decide and then act… I will have to know, for sure, whether or not I can kill my pigs… I don’t think I do know… I’ve shimmied and waffled….

Oh do get on with it!

She does, eventually. Big Pig and Little Pig are butchered in time to supply roast pork belly ‘with a magnificent pile of crackling’ for Christmas, plus enough joints and sausages and charcuterie to satisfy even a Spaniard for many months — and a giant pork pie. After all that dithering, the carnivorous instinct triumphs.

Not so for Pía Spry-Marqués. In a startling postscript she reveals that ‘all those chorizo days are now far behind me’: writing Pig/Pork has converted her to veganism.