After failing with 1S05 07:00 Kings Cross to Edinburgh in the Knebworth area 91117 had to be removed from the train and dumped in Langley Redlands sidings. This required the Kings Cross Thunderbird to attach to the south end of the train and haul the set from the Down fast using the emergency crossover to the north of Stevenage station and back to Langley Junction. There the set was reversed into the sidings, the 91 detached and the MkIV set returned to Bounds Green.