The British Rail Mark 4 is a class of passenger carriages built for use in InterCity 225 sets on the East Coast Main Line between King's Cross, Leeds and Edinburgh. Withdrawals began in 2019, with some being sold for further use with Transport for Wales between Cardiff and Holyhead. History and construction A small build compared with the Mark 2 and Mark 3 designs, 314 Mark 4s coaches were built between 1989 and 1992 by Metro-Cammell's Washwood Heath factory to operate services on the newly electrified East Coast Main Line. They were operated by London North Eastern Railway and its predecessors in 30 fixed formations of nine carriages, with a Class 91 locomotive and Driving Van Trailer. The Mark 4 is an all-steel coach incorporating a number of improvements over the Mark 3 stock - notably the inclusion of automatic push-button operated plug-type doors, in place of manually operated slam-doors, fully sealed gangways and controlled emission toilets (CET). Body shells were built by British Rail Engineering Limited (BREL) and Società Italiana Ernesto Breda. After a period of evaluation in 1988, Swiss SIG type BT41A bogies were selected rather than BREL Type T4 bogies when BREL could not provide commercial guarantees on the demanding lateral ride comfort required for running (BT41B/C refer to the bogie types used on the Mk4 DVT). However, during the first year of operation in 1989, complaints were made about the "lively" ride of the coaches. This required modifications to the damper and spring rates of the bogies and the fitting of inter-coach car coupler dampers to improve damping between the vehicles. Disabled access was another priority of the design, so the door vestibules were enlarged to allow a more generous turning circle for a wheelchair. With ever-increasing levels of overcrowding, the so-called 'gangway passenger' had become an important consideration, so the vestibule environment was improved with carpeted walls, better lighting, sealed gangways and carriage doors plus four flip-down seats per vestibule (since removed and replaced with bench style perch seats). Many of these innovations came courtesy of the abandoned Advanced Passenger Train, upon which the Mark 4 was heavily based. This influence was most obvious with the profiled sides, intended to allow the retrofitting of tilt-equipped bogies derived from the APT. This would have allowed up to 6° of tilt; modified coaches would have been designated Mark 4 T, but this plan was abandoned in January