Channel Tunnel: the facts

The Channel Tunnel was officially opened by the Queen and France's then President Mitterrand on 6 May, 1994.

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* The tunnel is 50 kilometres (31 miles) long, with the 39km (24 miles) undersea section being the longest undersea tunnel in the world.

* The service tunnel - the only one of its kind in the world - also acts as a "safe haven" maintained at a higher air pressure and thus remaining free from smoke and fumes.

* On average, the tunnels lie 40 metres below the seabed of the English Channel.

* Eurotunnel shuttle locomotives are among the most powerful locomotives in the world - generating up to 7,500 horsepower and hauling trains of up to 2,400 tonnes at speeds of up to 85mph.

* Tunnelling began in December 1987 using giant boring machines which advanced at up to 75 metres a day.

* The two single track rail tunnels are 25ft wide and there are cross passages every 375 metres to link them to the service tunnel.

* When the two halves of the first tunnel met undersea in autumn 1990, they were a mere four millimetres off the line plotted by surveyors.

* The concrete which lines the tunnels is the strongest in the world with a crushing strength twice that of concrete in nuclear power stations.

* More than 20 million tonnes of "spoil" were removed from the tunnel and used to create 73 acres of new chalk grassland on the Kent coast.

* More than 125 miles of rail track was installed with a sub station powerful enough to provide electricity for 250,000 people.

* Over 170 million man hours were spent building the tunnel.