While passengers can take their personal cars, they cannot drive them through the tunnel; instead, vehicles are loaded onto specially designed shuttle trains.

The chalk is composed of millions of microscopic algae shells, known as coccoliths, that sank to the ocean floor during the Late Cretaceous period.

Around 450,000 years ago, an overflowing glacial lake shattered the chalk ridge connecting Britain to mainland Europe, permanently severing the landmass.

At just 21 miles wide, this narrow gap allows people standing on the English shore to clearly view the buildings and lights of France on a clear day.