The Leader class basically was a disaster. Nothing like this has ever been built before. Numbered 36001-36005, it had been designed by Oliver Bulleid (who made the Q1 0-6-0 and the WC, B of B and MN 4-6-2 classes) it weighed 130 1\2 tons rather than the proposed 110 t ons. The driver and fireman were separated from each other in cabs at each end of the locomotive.
The fireman's compartment was where temperatures 50 degrees Celsius were recorded. Consequently, trial runs had the No.2 end leading because the cab was not too hot. Also, the 0-6-6-0T was too high for the water column which led to a copper chute and a leather bag having to be carried on the locomotive so it could use them.
When the project was scrapped, 36002 was only days away from steaming, 36003 was largely complete and 36004 and 36005 were basically frames and a boiler temporarily mounted on a rolling chassis. These were all scrapped.