The foundation stones of world theatre are cracking. We report that modern productions are destroying the ancient open-air theatres where Aeschylus, Sophocles and Euripides developed tragedy, and Aristophanes pioneered comedy. Most of them are in Greece, though colonists spread them around the Mediterranean. Some are 2,500 years old. Their performances have profoundly influenced theatre, literature and culture. But they cannot cope with the stresses imposed by modern audiences.

This is odd, for these are not fragile structures. They are vast circular arenas seating many thousands, and constructed of local marble and granite: think of Stonehenge rather than Crystal Palace. They have withstood the stamping of the chorus in the dythiramb, and the bellowing of the protagonist and deuteragonist from behind their masks. The actors wore high-heeled boots called cothurni the better to stamp with. Here Agamemnon's bloody corpse was rolled out on the trolley, and gods and goddesses were swung into view by the crane. Here the maddened Bacchae screamed iambics as they ripped King Pentheus apart. Miscarriages and deaths were reported when the Erynies (Furies) thundered on stage to purge the audience through pity and terror.

But none were as destructive of old stones as amplifiers, chewing gum and high heels at modern “cultural events”. Ancient theatres are built to have perfect acoustics, so they are not suitable for pop concerts. Ushers should confiscate chewing gum. And even fashionistas should be made to put on slippers for the tragedy. The homes of theatre must be preserved for live performance, not shrouded as dead monuments.