When trains started to slip backwards they created a series of horseshoe-shaped tunnels, ascending at a more gradual gradient.

So many people work hard merely to stay still while even more slip backwards.

The train proceeded 600 yards into the tunnel but then began to slip backwards, as shown by skid marks observed afterwards on the rails.

As the trawl continues along the seabed, fish begin to tire and slip backwards into the net.

Ladders can also slip backwards owing to faulty base pads which usually fit into the ladder stiles.