had British Railways livery. Ivatt 'filed' all correspondence from British Railways instructing the removal of the LMS letters, which were finally removed only upon his retirement, in 1951. On 14 and 15 January 1948, No. 10000 underwent tests on the line between St Pancras and Manchester, the schedule being set to timings based on a standard 4-6-0 (5X) passenger express locomotive. The attached load was a 393-ton tare, 12 carriage train including a dynamometer car; No. 10000 performed the services within the accepted schedule. Operations After initial tests, from February 1948, locomotive No. 10000 was placed on a twice-daily London-Derby (128.5 mile) return passenger service, hauling trains of 300 to 450 gross tons. No. 10001 also began service on the London-Derby route when completed, with a Derby-Manchester service also begun. In late 1948, both units were withdrawn for modifications based on service experience. They then returned to their midland service, before being transferred to operate express Euston-Carlisle-Glasgow passenger trains. The locomotives were operated in multiple: on 1 June 1949, they operated the 16 carriage "Royal Scot" express of 545 gross tons non-stop from Euston to Glasgow, making a return run on 2 June. At the gradients leading to Shap and Beattock, the engines operated at full power, hauling the trains at 38 and 36 mph in each case. After June 1949, the units operated for over two months in multiple formation - working London-Carlisle and later London-Glasgow services. In multiple, the locomotives showed potential for high speed services, on one occasion operating a standard Euston-Carlisle train at an average speed of just over 60 mph, including delays; this was 74 minutes quicker than usually scheduled. From mid 1949, the locomotives began operating singly, with No. 10000 worked Euston-Blackpool services, and No.10001 was trialled operating London-Glasgow services. Other services operated included London to Crewe and to Liverpool. On the "Red Rose" express, No. 10001 recorded 82 mph on a down gradient with a gross train load of 490 tons. The units were also used on freight services, including express London (Camden) to Crewe, and Crewe-Willesden; the locomotives met the scheduled average speed of 45 mph on the Camden-Crewe trains with a 500-ton train. One notable freight working was the haulage of a 60 wagon, 1,100 ton gross coal train, between Rugby and Willesden, achieving 25 mph on a 1 in 133 gradient to Tring Summit. Other operations included a trial on