Peter Kerslake says "10201 was completed at Ashford Works in 1950 following the Southern's late foray into diesel traction for express passenger work. It had an upgraded English Electric 16-cylinder engine of the same design that had had been fitted to the LMS diesels 10000 and 10001 but producing an increased horsepower of 1750. In April 1955 both 10201 and 10202 were transferred to the London Midland Region, to be joined by 10203 three months later."