The signaller was unaware that the automatic warning Warning system , which warns Warning drivers of adverse signals , had been turned off Being_in_operation in the cab of the express Expressing_publicly , and had set Placing a route which would stop Preventing_or_letting the express and allow Preventing_or_letting the freight train to cross Motion_directional in front of it .

The passenger train operating Being_in_operation company had contravened Hindering the rules in failing to inform Telling Railtrack and the signaller that the safety system was inoperative .

The signaller at the south end Process_end of the tunnel belatedly waved Body_movement a red flag in an attempt to stop Preventing_or_letting the second train , but thought that it had not been seen Perception_active .

The signaller then misinterpreted a 'line clear ' telegraph message from the signal box at the north end Process_end of the tunnel as referring to the second train instead of the first , and signalled Communication the third train into the tunnel .