The British Rail Class 423 (or 4Vep (Vestibuled Electro-Pneumatic brake)) electrical multiple units were built by British Rail (BR) at York Works from 1967 to 1974, although the MBSOs and TSOs of the first 20, 7701-7720, were constructed at Derby Works. They feature manually opening doors next to every seating row and were the last coaching stock built in this pattern for BR.