in order to work with the trains used on the Bognor Regis services, suitable for airport link use because of their larger luggage space.

This situation lasted until the early 1970s when increased passenger and luggage travel to the station was rendering the old system obsolete. British Rail therefore decided to adapt a number of Class 423 4VEPs with increased luggage capacity (at the expense of fewer second class seats) and were redesignated as Class 427 4VEGs.