The Southern Railway designed a main line diesel prior to nationalisation but lost the 'race' to get the first one into service to the LMS by three years. The three locomotives, Nos 10201-3, were transferred from the Southern to the London Midland Region in 1955 and came under Derby’s care for maintenance. No.10202 entered Derby Works on 30th January 1956 for a Heavy General overhaul and finally returned to traffic in November, after 249 weekdays out of service. Its Engine History Card records that it had an "Alteration to housing roof" at a cost of £107. Derby had taken over its overhauls from late 1955 following its transfer to the London Midland Region from the Southern Region in April of that year.
No.10202 was photographed on 18th November 1956 newly repainted in British Railways green with the post-1956 emblem, having spent its early years in black livery. The three Southern diesels were in many ways the fore-runners of the English Electric Type 4s which had the same engine and the eight wheeled bogies with one pair merely idle carriers of the great bulk of these locomotives.