The Pep Stock were prototype electric multiple units used on British Rail's Southern Region during the early 1970s. They were forerunners of the BR Second Generation electric multiple unit fleet. Three units were built, one two-car unit (2001), and two four-car units (4001/4002). Under TOPS, they were allocated Classes 445 (4-Pep) and 446 (2-Pep).

Internal layout was for commuter services; low-backed, bus-style 2+2 seating in open saloons, wide gangways with hanging straps, and no lavatory facilities. They were the first electric multiple units designed by British Rail with electric sliding doors, outside the Scottish Region. They were unable to operate with any other stock due to their new coupling system. Externally, 2001 was finished in unpainted aluminium, while 4001/4002 were painted in all-over Rail Blue. In passenger use, they normally operated together as a ten-car formation.

The production-run classes which are most visibly similar to the Pep Stock are the dual voltage 750v DC/25kV AC Class 313, the 25kV AC Classes 314 and 315, and the 750v DC Classes 507 and 508. However, subsequent builds have also drawn heavily on the experience gained by this stock.

Departmental Use

After the units were withdrawn from passenger service, they continued to be used by the Research department for further tests. For ths purpose, the units and individual carriages were all renumbered into the departmental series. Two power cars were teamed with a newly built trailer and became TOPS Class 920, number 920001. The remaining cars were formed into two four car sets and became TOPS Class 935, numbered 056 and 057 in the Southern Region departmental (non-revenue earning) unit series.

Disposal

All three units were finally taken out of use in the mid-1980s. Unfortunately, none of the cars have survived; 920001 was scrapped in 1987, 056 in 1986 and 057 in 1990.

Formations

The unit formations in passenger and departmental service were: