It becomes very hard to reverse this process and lock the metals up again, although it can be done.

FORBES: Fracking With Bad Water

Chris Hall, of the Rail Accident Investigation Board, said that Mr Lund would have had "no reason to believe" the train would change direction, which was most likely caused by the driver forgetting to lock the reverse lever.

BBC: North Yorkshire Moors Railway death: Family to sue

The new standard of practice is to lock down the camera and move the action around it, instead of the reverse, which is the case in today's 2D movies.

CNN: Why I can't watch 3D TV