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Drivers said a safety device, known as "a dead man's handle", failed to activate and stop their trams.

Another driver told the BBC of a dead man's handle failure in May 2016.

On some lines, the continued use of older trains means that drivers themselves use a lever known as the "dead man's handle" to move them between stations.

I dropped the dead man's handle, the train started to slow and then I saw him jump.

Suddenly the automatic signals went from green to red, the Duke of Kent removed his hand from the "dead man's handle" and the trainload of ordinary passengers, who had no idea who their motorman was, screeched to an abrupt automatic stop.