 The sequence in which Burt Lancaster evades an air attack on his  locomotive by driving at full speed into a tunnel was based on an  attack on the Great Western Railway during the war. A passenger  train was pursued by a German aircraft along the main line into  Wales. Reaching speeds estimated at 90mph (well above the wartime  restrictions in place) the train successfully escaped into the  tunnel under the River Severn in Gloucestershire and stopped beneath  the river until the driver judged that the danger had passed. The  train was struck several times during the chase but there were no  serious injuries.