As lunchtime approaches at Il Tirreno, a private beach club in Montalto di Castro on the Lazio coast, Beatrice Bordo, sitting in the shade of a blue umbrella, unwraps a slice of pizza.

A pranzo al sacco, or packed lunch, has become the latest skirmish in Italy’s long-running beach disputes after a woman was confronted over the clandestine consumption of a homemade sandwich at a private establishment in Puglia.