4-car EMUs, originally built 1967 to 1974 by BR York works. Numbered 7701 to 7894. Southern Railways designation 4VEP (Vestibule Electro-Pneumatic Brake).
Refurbished from 1988 on and renumbered to 3401..3591 (class 423/1, 4VEP), 3801..3812 (class 423/1, 4VEP), 3813..3844 (class 423/8, 4VIP) and 3901..3919 (class 423/9, 4VOP). 4VIP (Vestibule Intermediate Plan) and 4VOP (Vestibule Open Plan) are refurbished units operated by Southern.

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