In early 1948 the newly formed British Railways ran a series of Exchanges which compared the performance of selected locomotives from each of the former companies by running tests in normal service over selected routes on each region. The locomotives chosen were divided between those used on express passenger work, freight work and 'mixed traffic' services, and the Black 5 'competed' with an LNER B1 4-6-0, a GWR Modified 'Hall' 4-6-0 and a Southern 'West Country' 4-6-2. 45253 from Kentish Town represented the Class. To say that the performance of 45253 over the first two routes in the series was well below the 'norm' expected for the Class was something of an understatement. Its nadir was on the ex-Great Central route from Marylebone to Manchester via Sheffield Victoria, where it is pictured. 45253 managed to arrive 34 minutes late on its first run and only improved slightly to be 18 minutes late on its second attempt.