The BR Class 42s are diesel-hydraulic locomotives that were built from 1958 - 1961. Class 41s and Class 43s (Not to be confused with the diesel-electric locomotive) are also Warship classes. They have the Bo-Bo configuration where they have four axles, and two individual bogies.
They were developed and introduced in 1958, and a total of 38 Class 42s were built from 1958 - 1961. The only surviving Class 42s are D821 and D832. By the end of 1972, the Class 42s have been withdrawn from service, and they retired through 1968 - 1972.