The Channel Tunnel is known as one of the wonders of the Modern World.

Albert Mathieu’s 1802 original idea for a tunnel for horse-drawn traffic, lit by oil lamps, had to wait 250 years to come to fruition.

This marvel of engineering was constructed by an Anglo-French consortium called TML (Trans Manche Link) for their client Eurotunnel.

The two railway tunnels and smaller interconnecting service tunnel took seven years to build.

Between the two terminals at Folkestone and Calais, the tunnels are 51km (31 miles) long. For 37.5km (24 miles) the Channel Tunnel runs 50m below the seabed, yet when the French and British tunnel boring machines met in the middle, they were just 5.8cm out.

The tunnel was officially opened in 1994 by Queen Elizabeth II and French President François Mitterand.

Today, despite two million cars and seven million people travelling through the tunnel each year, this immensely expensive enterprise  - it cost £10 billion -  is still operating at a loss.