 36001 was shown to have several flaws, including heavy coal and water consumption, mechanical unreliability, untenable working conditions for both fireman and driver, loss of steam through the cylinder rings and uneven weight distribution on the bogies.After renewing the cylinder assembly, it was tested around Brighton and Eastleigh using an LNER Dynamometer car, where good running was experienced at high costs in fuel and effort on the part of the fireman.For a period of two weeks the Leader was tested against the performance of a U class locomotive which indicated that the brake release was too slow in service for use on tight schedules despite the brake application being noted as the best used on a Bulleid design.