The Class 25 (TOPS designated from 1971) diesels introduced in 1961, were a developed of the earlier Class 24 Bo-Bo diesels introduced in 1958. Following publication of the British Railways Modernisation Plan in 1955, a number of diesel types were built within defined power ratios. The Class 25's were rated as Type 2 locomotives and if it was necessary to provide more power, then they worked in pairs, particularly in heir latter years. The Class 25's were, however, a true mixed traffic locomotive and were equally at home on passenger, freight or parcels duties. Despite only being a Type 2 locomotive, the Class were well suited to replace steam traction on duties over a wide area of the British Railways system. Locomotives were allocated to depots across the Eastern, London Midland, Scottish and Western Regions. Although not allocated to the Southern Region, they were often ssen on workings from other regions. Closure of many lines in the 1960's resulted in the loss of a considerable amount of passenger work and the class were more likely to be found on parcels, newspaper ot freight duties.