Leading edge technology that came unstuck inside a tunnel

Eurostars are the most technically complex trains run in Britain. At £24 million each, 18 coaches and a quarter of a mile long, they contain a mass of electronics.

With the sloping nose power car at each end - they can operate in push-me pull-you mode - they are designed to cope with the power supplies and signalling systems of the three countries which run the service, the UK, France and Belgium. They travel at up to 186mph and can seat up to 770 passengers - the equivalent of two fully loaded Boeing 747s.

There is a crew of up to 19 per train, a driver, two managers and up to 16 catering staff.

One of the managers is also a qualified driver and can take over in the event of the duty driver becoming unwell.

When launched in 1994 they were described as being on the "leading edge of rail technology." Unfortunately it is their complexity which has led to problems.