How the Channel Tunnel Was Built

For almost two hundred years, people dreamed of traveling between Britain and France without getting on a boat. In 1802, a French engineer proposed a tunnel lit by oil lamps, through which horse-drawn carriages would travel. An artificial island would be built halfway across, so that the horses could be changed. The plan was presented to Napoleon, but war broke out again between the two countries the following year, and nothing was done.

Other plans followed. In the early 1880s, digging actually started on both sides of the Channel, and more than a mile of tunnel had been dug from the English coast near Dover before the work was stopped. British military leaders had become convinced that an enemy army could use the tunnel to invade the country. A second serious attempt was made in the 1970s, but it was abandoned in 1975, when the British government decided that the project had become too expensive.

The decision that finally made the tunnel possible was taken in the 1980s. In 1986, the British prime minister, Margaret Thatcher, and the French president, Francois Mitterrand, signed the Treaty of Canterbury, in which the two countries agreed to build a fixed link. Several designs had been considered, including bridges and road tunnels, but a rail tunnel was chosen. The British government insisted that no public money should be used, so the project was paid for by private companies, banks and investors.

Construction began in 1988. In fact, the Channel Tunnel is not one tunnel but three, running side by side: two rail tunnels, one for each direction, and a smaller service tunnel between them, which is used for maintenance and emergencies. They were dug through a layer of chalk marl, a fairly soft rock that is easy to cut and does not let much water through. Eleven enormous tunnel boring machines were used, some starting near Dover in England and others at Sangatte, near Calais, in France.

Digging from both sides meant that the two halves had to meet in the middle, deep under the sea. The machines were guided by lasers and careful surveying, and their route had been calculated so precisely that, when the service tunnel was broken through on 1 December 1990, the two sides were less than half a meter out of line. A British worker and a French worker shook hands through the gap, and the moment was shown on television in both countries.

The rock that had been removed had to go somewhere. On the English side, millions of tonnes of it were placed at the foot of Shakespeare Cliff, near Dover, where a new piece of land was created. Today it is a nature park called Samphire Hoe. The work was also dangerous: ten workers lost their lives during construction.

The tunnel was officially opened by Queen Elizabeth II and President Mitterrand on 6 May 1994. It is about 50 kilometers long, and almost 38 of those kilometers are under the sea, which makes its undersea section the longest in the world. By the time it was finished, it had cost around 80 percent more than had originally been estimated.

What did it change? Before it opened, ferries and planes were the only ways to cross. Today, high-speed trains carry passengers from London to Paris in a little over two hours, and shuttle trains carry cars and lorries between Folkestone and Calais in about thirty-five minutes. Millions of people make the journey every year, and many of them hardly notice that they have passed from one country to another beneath the sea. The tunnel that had been imagined in Napoleon's time had finally been built, by machines that its first planners could never have imagined.