Twenty years ago, Queen Elizabeth II and President Francois Mitterrand braved the drizzle to cut the inaugural ribbon of the Channel Tunnel, realising a centuries-old dream of linking France and Britain under the sea.

A prodigious industrial adventure, the project mobilised 12,000 engineers, technicians and workers to create the world’s longest underwater tunnel nearly 38km from northern France to southern England, earning it the “Global Engineering of the Century Award” by the International Federation of Consulting Engineers. But this tour de force, officially inaugurated…