Plus 1392 to 1399?
South West Trains inherited a small fleet of twelve 'Phase 2' 4Cig units, and the larger fleet of 22 "Greyhound" units which had been modified to allow faster acceleration.
In 1997 the fleet was augmented with the addition of eight 4Big units from Connex South Central. These operated with the counter in the buffet carriages locked out of use. By 1999 these units had been stored, but then eight additional "Greyhound" units were converted from the redundant 4Bigs. The units were reclassified as Class 421/8, and renumbered in the range 13921399. The modifications included the removal of the buffet carriages, which were replaced by spare intermediate trailers from 4Cep units. Most of these trailers came from 4Cep units to make 3Cep units, but a few came from withdrawn units. These trailers were immediately recognisable since although they had the same body profile as the rest of the unit the windows were different and they had InterCity70 seating. The buffet carriages were withdrawn, although many were saved for preservation.
Lifted from Wikipedia.