They have manually opening doors next to every seating row and were the last coaching stock built in this pattern for BR.

Ordered in 1965, 194 standard four-car 4 VEP units were built between 1967 and 1974, numbered 7701-7894; subsequently becoming class 423 under TOPS.

The work involved fitting fluorescent lighting and public address equipment, and also rebuilding the MBS (motor brake second) vehicles with an additional two bays of seating in space formerly used for luggage.

In 1968, due to a shortage of suitable stock for the Bournemouth electrification scheme, BR formed an eight-carriage 8 VAB unit, no.

The 'TRB' vehicle retained its gas-powered appliances so, unlike 4 REP buffet cars, was able to provide hot food and beverages while on diversions away from third-rail areas.

Adjacent MBSO 62203 had most of its doors locked out of use and tables fitted across them for the service of meals on a 2-and-2 basis (across seats intended for five persons normally); this vehicle also had most of its luggage racks removed.

7788-7799, were fitted with extra luggage racks by removing the squabs and cushions from certain seats and reclassified as Class 427 4 VEG units.

Externally these units were marked by an orange/yellow (dayglo) coloured band at cantrail level with lettering 'London-Gatwick express service'.

Following the privatisation of British Rail the three southern train operators all inherited large fleets of 4 VEP units.

[citation needed] The Network SouthCentral division inherited a fleet of 50 standard Class 423/1 units.

The franchise was originally won by Connex South Central, which soon applied its yellow and white livery to the fleet.

However, following poor levels of service and financial mismanagement, the franchise was transferred to South Central Trains in 2000, which was later renamed as Southern in 2004.

In 1998-1999, whilst still under the control of Connex, 19 units were modified to operate inner suburban South London "Metro" services.

Due to the lack of first class seating and toilets, these units were generally not used on long-distance services.

The following Saturday saw the final slam door trains on Southern, when units 3490, 3505 and 3535 formed the 09:19 Brighton to London Victoria and 11:06 London Victoria to Brighton services (via Lewes due to engineering works); this being the last scheduled mainline passenger service using southern-electric slam-door stock (the very last passenger being an off-duty HM Inspector of Railways).

These were also standard units, but were numbered in the 38xx series to denote they were leased from Porterbrook rather than HSBC Rail.

These four units were deliberately retained in NSE livery, meaning that in the final days of slam-door trains they attained "celebrity" status among rail enthusiasts.

In 2001, SWT placed an order for 785 new carriages with Siemens to allow it to replace its fleet of slam-door trains, in accordance with its franchise commitment to do so by 2005.

3417, into its original BR Blue livery to commemorate the final months in traffic of the slam-door fleet.

The final normal passenger service was operated on 26 May 2005 from London Waterloo to Bournemouth, using 4 VEP 3536 sandwiched between 4 CIG units 1396 and 1398.

The unit was initially used on Wimbledon depot as a shunter, but with SWT needing to get it off its books it was sold to the Bluebell Railway for the nominal sum of £1.

In late April, the unit sustained minor damage to its shoegear as it was being driven from sidings at Clapham Junction Yard prior to movement under tow to the Swanage Railway.

The unit was for some time stabled in the open at Clapham Junction, having previously been stored in the shed at the yard.

After the completion of this bodywork restoration, it was transferred to Strawberry Hill in South West London where the interior underwent long-term refurbishment by volunteers from the Southern Electric Traction Group.

The other half remained in "as withdrawn" Connex condition, and the set operated at several special events throughout that year.