[1][ii] Unlike the earlier Pilot Scheme, the BTC expected that these prototypes would be funded by the makers, rather than bulk orders being placed sight-unseen.

Lion used a more powerful development of the same engine as the Class 44 Peaks,[2] but lighter overall[iii] and with a more reliable bogie design.

The cooling group was provided by Serck and used two radiators in a removable pack in the roof over the Nº1 end and the Spanner Swirlyflow steam heating boiler.

This lightweight moulding could be raised upwards by pneumatic cylinders when stationary, to act as an air vent before needing access to the engine.

The livery stood out from other locomotives, although also showed dirt, as it was painted white overall with the side ribs picked out in gold.

BR tested it initially on Western Region services out of London Paddington based at Wolverhampton Stafford Road Shed.

Full details of Lion's final withdrawal have never been fully made public, and even the BRC&W workforce were not informed of its fate.

During this process Sulzer recovered their 12LDA28C power unit and radiators (the engine was sent to be reconditioned at Vickers in Barrow-in-Furness, and was subsequently installed into an unknown production Class 47).