It will be the longest combined road and rail tunnel in the world with a motorway, two railway tracks and a service and emergency corridor.

All four buildings were linked by a subterranean rail tunnel served by small steam locomotives.

Car shuttle trains commonly operate through a rail tunnel connecting two places not easily accessible to each other by road.

It was at the western end of the rail tunnel and was caused by floodwater coming from a nearby disused canal tunnel.

A cross channel rail tunnel was first proposed in 1802 and construction actually started in 1881 before being abandoned.