My Dad a loco fitter told me the longest passenger he ever saw was 32 coaches worked by a V2 during the war. It was 2 troop specials coupled together after one loco failed. The driver was Harry Gutteridge, he worked the train forward until another loco could be found, not at a great speed however. This was at Darlington working northbound, Harry patted the loco on the cabside whilst saying "come on girl you can do it. I wish we had properly recorded his memories.....