The class gained the nickname "Hoovers" because of the noise made by the clean air plant at the No.2 end, prior to refurbishment, which was likened to that of a vacuum cleaner, a name believed given to them by the staff at Paddington Station. Once the electrification from Crewe to Glasgow was completed the locomotives were moved to the Great Western Main Line (GWML) out of Paddington to allow the retirement of most of the remaining diesel-hydraulic locomotives then in use. As trains on the GWML steadily moved to High Speed Train operation from 1976, the Class 50s moved to hauling trains between London Waterloo and Exeter St Davids, and also trains from London Paddington to Hereford and Worcester via Oxford until the majority of those trains too were taken over by IC125 operation. The class was steadily retired from service in the late 1980s and early 1990s as their services moved to operation by second-generation Class 159 DMUs.