The picture shows the view from inside a tunnel that caved in over one of the main lines between London and Birmingham, at Gerrards Cross in Buckinghamshire.

Tesco was constructing the tunnel to allow a £20 million superstore to be built over the line, but a 50- metre section collapsed six weeks ago.

The picture was taken hours after the incident, which it is estimated will cost Tesco £20 million. Train services are still disrupted.