Costanzo Carta takes a big knife, cuts into a chunky wheel of tawny cheese and there they are, white and wriggling in a lively fashion: maggots.

“Try it, it won’t do you any harm,” he says, proffering a dollop of the stuff on the end of the blade.

This is casu marzu, a highly unusual delicacy from Sardinia that has earned a listing by Guinness World Records as “the world’s most dangerous cheese”.

To some, it is a proud symbol of Italy’s gastronomic heritage; to others, a stomach-churning abomination.

Either way, it is a tradition that is now in decline, to the regret of many Sardinians.

Shepherds deliberately allow a specific type of fly called piophila casei to enter the cracked rinds of the cheese wheels and lay their eggs.

The eggs hatch into maggots which slowly but avidly squirm and munch their way through the cheese.

Their secretions turn it into a creamy, pungent goo that is highly prized by aficionados. In the Sardinian language, casu marzu means “rotten” or “putrid” cheese.

There’s just one problem – it is illegal.