Well let's hope they don't make such a mess of it as the Tornado mob did, partly at least through an arrogant assumption that the old steam engineers didn't know what they were doing. Result: hollow stays that broke with temperature cycling, severe pincushioning of the firebox, and a year out of service when still brand new.

There's also a big threat on the horizon: ERTMS is proposed to be rolled out over many main lines in the next 20-25 years- it's already in place on the Shrewsbury- Aberystwyth/ Pwllheli line. This requires the signalling system to be able to control the loco, so the throttle and braking system if not the valve gear too will have to be able to be operated remotely. They will also have to make room underneath for the "balises", the signalling sensors, and sacrifice some tender space to the electronics.