Was the terrifying Sussex train crash caused by the heatwave? Passenger carriages came off 'buckling track in extreme heat' in Lewes, transport expert says

Three train carriages left the tracks on an embankment near Lewes, leaving 20 people injured.

The eight-carriage train came off the line between Haywards Heath and Lewes at around 3.54pm this afternoon, with services set to be cancelled until 10pm.