Built from 1964 onwards these 4 car units have one non-driving motor unit, a trailer second and 2 non-motor driving units. Maximum speed is 90 mph, 145 km/h and have 4 185 kW motors rated at 740kW, 992 hp. They pick up current via a 3rd rail at 750 V dc. Originally designated 4CIG by Southern Region, these 4 car express units became class 421/4. The sets are powered by a 740 kW, 992 hp non-driving motor brake second and have a 90 mph, 145 Kmph top speed. Class 421/4 use mark 6 motor bogies while class 421/3 use the older mark 4 design.
Unit 421866 at Eastbourne, Sussex in platform 2 on a damp Sunday morning June 6th 1999.