The idea of joining England and France by means of a tunnel is by no means a new one.
A couple of engineers proposed a tunnel to Napoleon: in 1802, Albert Mathieu wanted to build a tunnel for horse-drawn carriages, with an island half way for ventilation and changing horses; and in 1856, Aimé Thomé de Gamond suggested it again.
But neither scheme came to anything.
The first serious attempt at construction came in 1881. A 1,893-metre pilot tunnel was dug from Shakespeare Cliff, and a 1,669-metre tunnel from Sangatte.
That endeavour was abandoned in May 1882 after the British government got cold feet, worried about the French using it for nefarious invasion purposes.
After Britain joined the Common Market, the British and French governments decided to have another go. And so in 1974, work started on both sides of the Channel on a publicly-funded project. But, short of funds, the British government cancelled it in 1975, after about 1,400m of tunnel had been dug.
In the 1980s, the now Conservative government declared it had no objection to a privately funded tunnel being built. And so in 1988, work began for a third time. This time, it would be a two-bore rail tunnel, with a smaller service tunnel between them.
Two years later, on 1 December, Graham Fagg and Philippe Cozette broke through the service tunnel and shook hands 40m below the sea bed, 14 miles from the English coast and ten from the French. The breakthrough had been made.
Work continued on the main tunnels for another six months. 13,000 engineers worked with 11 tunnel boring machines, digging 76m a day. The north tunnel broke through in May 1991, and the south tunnel in June.
The completed tunnel is 31.4 miles long – only 23.5 miles of that is under water. It cost £4.65bn – 80% more than originally estimated.
It was officially opened by the Queen and President Mitterrand of France in May 1994.