system, surviving units from the range 6001–6042 were renumbered into the 42xx series (class 414/2); the surviving units of 6043–6173 became 43xx (class 414/3). Withdrawals of the class began in 1982 and modernisation of the units began in 1983, when 10 DMBSO from withdrawn units were converted for use on the Gatwick Express service in conjunction with converted loco-hauled Open First (FO) and Open Second (SO) vehicles and class 73 locomotives. These vehicles were classified as with "units" numbered 9101–9110 and individual carriage numbers 68500–68509. Accidents and incidents On 16 November 1970, a unit of the class was derailed at . On 26 February 1971, a train formed by five units of the class overran the buffers at , Kent. One person was killed and ten were injured. Preservation Two complete units have been preserved; (with a further four driving motor coaches, see ): References Sources Further reading 414 Train-related introductions in 1956 750 V DC multiple units