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

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

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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.

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Mr Ash said it was possible he did not lock a reversing lever into place, which could have prevented the locomotive from slipping between forward and reverse.

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Mr Ash, a retired professional train driver with more than 50 years' experience, said it was possible he did not lock a reversing lever into place, which could have allowed the locomotive to slip between forward and reverse.

BBC: North Yorkshire Moors Railway death: Family to sue