A total of 40 three car units are in use (numbered 001–040), of which 38 were delivered starting in 1999, although due to teething problems, they did not enter service until 2001.

Initially, a total of thirty 4-car units were built, with deliveries beginning in 1998, with the full complement in service by 2004.

However, they suffered from leaky roofs and failing electronics and were therefore stored from 2004 to late 2005, being replaced by more Class 450 units on the routes they operated.

[citation needed] During March 2021 SWR cancelled the withdrawal plans of their 458s and instead returned their Class 442s to their lessor.

SWR cited that 458s would be their replacement The Class 460 Juniper electric multiple units (also known as 8GAT) were originally built for use on the dedicated Gatwick Express airport service to London Victoria.

Following their removal from the Gatwick Express franchise in September 2012 a decision was made to reform and merge the Class 460s with the Class 458 vehicles in order to form 36 x 5-car trains to boost capacity on the South West Trains network.