Southern Railway publicity photograph
photograph: Glen Woods collection

The 4 Sub designation first appeared in 1941 for a new class of suburban unit first put into service on the Victoria to Orpington line. Two motor brake second compartments sandwiched two trailer second compartment coaches, one of which had been designed as a composite. They were built with steel underframes and body panels, timber frames supporting the body panels and with canvass roofs. This generation of 4 Subs had domed cab fronts and in that respect were similar to the 2 Hals.

Additional sets were formed from class 1285 3 Car Suburban Sets, with a Bulleid coach inserted to strengthen them to 4 coaches. Note that these three coach sets had not been referred to as '3 Sub'!

Southern Railway publicity photograph
photograph: Glen Woods collection

A further generation of 4 Subs was introduced in 1946. Built with flat cab fronts and curving bodywork along the lines of the contemporary Bulleid mainline coach stock, they were of all steel construction. These 4 Subs were however mechanically and electrically similar to the earlier batch. Again the coaches were all compartment, albeit slightly wider and more comfortable, and one trailer was also designed as a composite. A later batch introduced in 1948 had one trailer fitted with compartments but otherwise now had all saloon accommodation. The last batch was built in 1952.

4 Sub units were reformed over their lives, composite trailers being withdrawn and later saloon coaches replacing withdrawn earlier compartment stock. Withdrawal of undamaged units commenced in 1972 and all were out of service by the end of 1983. The 4 Subs were classified as class 405 under TOPS, but their unit numbers always remained under their original SR designation in the 4xxx series and were never renumbered into the 5xxx series to conform to TOPS.

British Railways Southern Region publicity photograph
photograph: Glen Woods collection