The British Rail Class 423 (4 VEP), electric multiple unit passenger trains were mostly built by British Rail (BR) at York Works from 1967 to 1974, although the MBSOs and TSOs of the first 20, 7701-7720, were built at Derby Works. They have manually opening doors next to every seating row and were the last coaching stock built in this pattern for BR. They were mostly found working outer-suburban services in South London and rural services in Kent, Sussex and Hampshire, up to 2005. The fleet had a working life of 38 years.

So far two complete units and two individual driving trailers have been preserved. In addition, the former 4TC driving vehicle from set 3582 has been preserved.