Forgot to mention in my last post that of first generation of diesel loco's was for the size and weight the power output (HP) was quite mediocre compared to that say of a coronation or A4 steam loco, hopes were high on improving passenger services and timings and they were pressed into front line service with little development when it would have been better to put them on freight services instead. Probably the biggest Achilles heel of this strategy was not helped by the fact that passenger rolling stock at this time was steam heated, no problem for a steam loco just tap off a supply from the boiler, but in the case of a diesel a steam generator had to be installed in the engine room, which obviously led to further complications and source of breakdowns. These were not a boiler as such but more of a series of coils heated by a fuel oil burner with water pumped in one end and steam coming out the other, only two manufacturer's supplied these, Stones Vapour and Spanner, and both were as bad as each other and were never ever reliable even to their end of use on the system, the thing was that if the boiler did'nt work then usually the whole loco was certified a failure and again sat around awaiting attention of the fitters. I've worked on the Stones and it was a right pig with it catching fire always a potential threat, you would start it up and it would'nt light let it go through the cycle and try again and it still would'nt light then all of a sudden it would take with a bang as the unburnt fuel that was dripping everywhere went up.
New blood was brought in from the automotive and aero industries as a new approach to design and build the experimental APT (much to the disgust of the established BR engineering hierarchy) which used hydraulic systems to control the tilt mechanism, but when the production series was commenced this team was quickly disbanded. BR engineers used a compressed air system to work the suspension which was harder to control incrementally and suffer from freezing up in cold temperatures, also the equipment used although proven in industry was not able to cope with the rigours of rail traction environment. Despite this they did well remember at the time there was no digital computer or micro processors then everything was the old analogue system, I was a great shame that this project was not put into storage for a few years until the electronics technology could catch up and I remember seeing on TV when they showed gangs of blokes, smashing the 3 or 4 sets of trains that had been built, up with sledge hammers what a waste even though the whole project only cost £50 million.