It’s safe to say that few people outside of Piedmont know where Carmagnola is. The name is vaguely familiar to Italian schoolchildren thanks to Alessandro Manzoni’s 1820 tragedy about the famous Count of Carmagnola (beheaded by the Venetians for possible betrayal). But otherwise Carmagnola, a town of 30,000 people immediately south of Turin, is better known in France than in Italy.

Carmagnola sits beside the river Po and the pavements of the old centre are under long colonnades created by flared, squared columns. They look sturdy, almost defensive. Looming over the town are the white Alps to the west, but otherwise it looks like any other: identical housing estates in the suburbs, mostly 4-6 stories high, and beyond them industrial estates, monocultural fields and, near the river, dozens of gravel quarries.

Only a hundred years ago, the countryside here looked utterly different. Until the early 20th century dense forests of Cannabis sativa provided what was then most common fibre in Piedmont and Emilia-Romagna: hemp. Now, as I walk to the river, there are only fleeting clues to that culture. I sometimes see holes in the older stables and barns. The smaller ones much higher up were for birds, so the peasants could take an egg or two from the nest. But the lower, square holes just above head height were for drying fibres after maceration.

The plants grew fast, up to three or four metres tall in one season. When it came to cutting, peasants left a single, female fern every square foot or so, in the hope that her seed masts would provide oils and animal feed, possibly even lead to natural regeneration. But after harvest, the stalks were so tough it required weeks of labour to render them into a weavable thread. Voluminous with foliage and buds, they were left to soak in water for 7-12 days. Stones were used to weigh down fat, long bundles – as wide as a 50-year-old tree trunk – in ponds, lakes and rivers. The poorest peasants just used the dew, which meant the whole process took three times as long. The process was stinky as rotting vegetation always is, but slowly the resin around the woody stalks would go soft and mushy.

The stalks were then washed and hung to dry on poles inserted into those holes in the barn. The end product was smashed up (scavezzatura is the antique term) so that the fibres emerged from within the woody stalk. That was the hardest, dustiest work, providing a carpet of blond, soft chips and, it was hoped, those almost indestructible strings. They were then combed into slim tangles which were rolled into hairy rugby balls and sold to spinners and weavers.

There was always a connection between the river Po and hemp: water was needed for maceration, but hemp was also, like horsehair, used to caulk boats. There wasn’t a shortage of fibres: riverbanks also had long boulevards of mulberries whose leaves fed the silk worms and provided the luxury alternative to hemp. Hemp itself was the rougher option, mainly used to make rugged rope, bags and farmer’s outfits. It was the clothing of the peasants.

Almost certainly that’s why, in France, les Carmagnoles – the vertically-striped, yellow-and-red waistcoats made of Piedmont hemp – became the livery of those revolutionary paramilitaries, the sans-culottes. Its coarse fibres and double buttons suggested both a military uniform and agricultural authenticity and so, during the Terror, Piedmont hemp became synonymous with the die-hards of the revolution.

The carmagnole waistcoat even gave rise to a bouncy song of the same name, in which a cheerful melody mixes with blood-thirsty lyrics about relishing the sound of the cannons.

The reputation of hemp as a fibre has suffered various onslaughts in the last 100 years or so: the rise of cheap cotton, the beginnings of synthetic threads and, of course, the out-lawing of production because of the plant’s association with narcotic intoxication. But as recently as 1926, Italy was still cultivating 105,000 hectares of hemp, producing around 120 tonnes of fibre. Piedmont wasn’t, by then, the largest producer, but its proximity to Provence, and the superior quality of its fibre, meant that its hemp was regularly exported to France.

There are now, in Italy, only 1,500 hectares in the whole peninsula dedicated to production: just 1.4% of the area 100 years ago. But in some ways this small Piedmont town is still the capital of Italian hemp. Two of the EU’s ten recognised Cannabis sativa varieties for agricultural use are from here (Carmagnola B and Carmagnola Selezionata), and it’s here that Assacanapa – the umbrella organisation bringing together 700 or so Italian hemp farmers – is based.

There’s an almost evangelical zeal to proponents of hemp. Once they have dispelled fears around drug-use (the hemp used in agriculture is legal because it has only trace levels of Tetrahydrocannabinol or THC, the psychoactive constituent of cannabis), farmers long to tell you about all the uses for the plant: for clothing, construction (hempcrete), cosmetics, nutrition (both seeds and oils), serious medicine and drinks (aromatic teas and liqueurs). As everywhere else, Italy has an intensifying debate on the legalisation or decriminalisation of cannabis. But whereas in many nations such a move might seem radical, here it would be restorative.