Look down into the waters of the Venice canals today and there is a surprising sight – not just a clear view of the sandy bed, but shoals of tiny fish, scuttling crabs and multicoloured plant-life.

“The water is blue and clear,” said Gloria Beggiato, who owns the celebrated Metropole Hotel a few steps from St Mark’s square and has a view over the Venice lagoon. “It is calm like a pond, because there are no more waves caused by motorised boats transporting day-tripper tourists.