Back to another of my chestnuts - the APT - P in particular and a glance at the " E" for experimental predecessor.
The concept of tilting trains dates back some considerable time before even the APT- E (experimental, the single gas turbine version) made the light of day. 1970s technology was adequate for the APT-P , the prototype.
Only we didn't get a prototype, the first of it's type, we got six pre-production types, the class 370.
The crux of the matter lies in this very over ambition. Yes a gas turbine one off had been produced but it was a running laboratory using an already disfavoured power unit supply. Proof of concept was established. However what was needed was a single prototype of the APT-P and not a whole pre-production class.
Why not though, produce a further proof-of-commerciality if you like by having a viable class of APTs running actual passenger specials which reflected the belief in BR management that this was a faite accomplis, as before the HST and the Deltic and electrification had been. In the 1970s though and into the 1980s this arrogance would meet its match in an in patient, road-oriented Magaret Thatcher.
There are major issues with managing a project with six train sets: firstly you have a longer time for delivery and your overall budget is much bigger, despite being lower per unit than a single set. Secondly and most crucially, when you have something go wrong on one set which is serious, then you have to take all the other sets out of service (tests, PR visits and demonstration ADDEXs essentially) . Further to this you then have a very much larger burdon on resources and spare parts when you come to repair the problem or redesign the system.
The tilting system was somewhat problematic however all reports are that eventually this was solved to a level of reliability concordant with operational service. The braking system's design oversights would have been typical "punch list" items for the redesign between and APT- P single electric unit and any pre production run or actual production run (squadron)
Launching the train officially as an operational Faite Accomplis in a January was really just another example of project management not removing elements which could challenge the reliability of the project and its then key PR presentation.
This reflects on poor project management and too much power invested in decision making in BR in my opinion. Today if the railways were still public, or as with HST2 a public-private alliance, then the project would be subject to tender and also to an expert committee and nost likely the "quantum leap" from the APT-E to the electrified prototype would be managed by a single unit or in fact competing designs. Subsequently a fleet of pre-scale production models could have been established to introduce the trains such that the flagship services could be accelerated gradually and revenue returns on a 3 hour London-Glasgow, and shorter timings from Manchester, Liverpool and the West Midland towns on the WCML, services be assessed.