Derby Works introduced the first mainline Diesel to UK service with the production of LMS 10000 in 1947, although mainline diesels had previously been tested on post-Grouping main lines prior to being exported. When British Railways' Modernisation Plan of 1955 was initiated by a Pilot Scheme to identify the best features for a future standard diesel fleet, Derby Works upgraded the design to produce its Type 4 - later Class 44 - locomotive that ultimately spawned 193 locomotives encompassing 3 variants which powered trains throughout the UK network. Fred Kerr lived close to the Midland Main Line in Northamptonshire and observed the class from their introduction in May 1959 to their final withdrawal in the 1980s and has amassed a collection of images showing them working both freight and passenger duties throughout the UK but particularly on the Midland Main Line where the Class 45 variant held sway for nearly 25 years. This album contains images from his extensive collection and, supported by a brief text, reflects the history of the 3 variants by showing the variety of services which they powered and the wide range of locations where class members were to be found.