In 1948, shortly after the formation of British Railways, the decision was taken to test locomotives from all of the former 'Big Four' companies to find the best attributes of speed, power and efficiency with coal and water. There were two ways of testing and comparing locomotives: either at the Rugby Locomotive Testing Station, which was not ready until late 1948 or by testing in the field itself. The results of the 1948 Locomotive Exchange Trials would be used to help design the British Railways Standard locomotives.