The first car emerged from GRCW's works on 22/4/58, and all were delivered between 5/58 and 7/58.
They entered traffic in May 1958 on the Leamington - Stratford, Birmingham - Dudley and Stourbridge Town - Stourbridge Junction routes of the WR.
On 25 August 1958 the class were introduced on the Ealing - Greenford branch. Several trains which had been withdrawn in the economy cuts of 30 June were reinstated from that date.
In September 1958 they replaced the AEC/GWR railcars on the Slough to Windsor branch. They also replaced these railcars on the Twyford to Henley-on-Thames branch, and steam push-pull on the West Drayton to Staines branch on the 6th October 1958. The 07:48 and 08:43 from Henley to Paddington and 17:15 and 18:15 returns remained steam hauled to retain a first class section.
Their original nickname was "coffin nails", as most of the routes on which they were used became victims of the "Beeching Axe" with closure usually soon after introduction. Lines such as Barry to Bridgend, Penarth to Barry, Snow Hill to Wolverhampton (LL), Worcester to Bromyard, Bewdley to Hartlebury and Didcot to Newbury. As these lines closed the cars were concentrated in the Bristol, Cornwall and Plymouth areas. Workings included local services over the ex-SR lines to Gunnislake, Axminster and Barnstaple.
In the 1970s some sets were re-allocated to Scotland, particularly around the Ayr area, with seven cars (2/5/7/11/13/14/15) being used. Three of these, 13/14/15 were converted to Class 131 DMLVs. The other cars - except 55001 which went into departmental use in 1969 - were later cascaded to the West Midlands based at Tyseley. They were used on local services, most notably the Leamington Spa to Stratford-upon-Avon route. One was for the Stowbridge Town - Jct shuttle and for fitting into formations when a car would be removed for depot or works attention.
In '84 two cars, 5/6, moved to LO to replace life expired Class 108s on the Stockport - Stalybridge service. The same year 4/9/11 were transferred to Bletchley for work on the St Albans and Bedford branches.
In 1987 problems with Class 142 units on the West Country branches resulted in a reprieve for six cars, 55000/3/5/6/9/12. The diagrams in the West Midlands were rearranged and the cars sent to Vic Berry's in Leicester for asbestos removal. Plaques were fitted to the solebars proclaiming this work was done.
The cars worked the Cornish branch lines to Looe, Newquay and St Ives until withdrawal.
The last two vehicles 55000/12 were withdrawn on 22/12/93. The two vehicles had spent their last days as motive power for Laira sandite vehicle 977466 (ex-Class 121 DTC 54286).