Wasn't it a bit like the Leader? They got the thing working to some extent, but nothing like what it was designed for?
They were prototype sets for a proposed fleet to completely replace the WC IC Loco-Hauled sets. I believe the later plan was for the power units to be the driving car/s rather than centre units as on the P. It would be speculation to say if the P units would have remained in service if the production fleet had happened.
Weren't there ride issues as well - pax feeling seasick? Not bashing the things - they're an icon of my childhood, which I was fortunate enough to see on shed and in action. Just not sure that they ever reached a standard that would allow them to grace the network again.
The travel sickness issue was caused by two things. The original specification was for the tilt action to completely counteract the lateral forces created by cornering. This was achieved but it was later realised that by doing so it made people more suceptible to travel sickness. This is due to the brain being confused by visual inputs of movement conflicting with the inner ear which is fooled into registering no movement by the tilt system.
The second issue was that the main problem with travel sickness was widely publicised by a bunch of journalists that BR had invited along to sample the train and subsequently plied with free booze. The effects of alcohol greatly enhanced the sickness and the journos took great pleasure in rubbishing BR and their new train leaving a public impression of the APT being an abject failure that it never overturned.
The first issue was solved by adjusting the tilt to not 100% counteract lateral movement which considerably reduces the problem. The second issue was solved by not inviting the aforementioned pieces of crap on to the train again.
It could be said that the ability to cause travel sickness was a confirmation of the success of the tilt mechanism.
All the major technical issues were sorted by the time the project was cancelled and the incredibly stupid PR based decision to scrap most of the stock was taken.
By that point the units had been running for several years alongside the regular trains with no fanfare and reasonable reliability.
I have no doubt that if a full unit in as withdrawn condition could be magiced up today it would have no difficulty whatsoever deputising for a pendo on a 2011 WC diagram.
Failing someone extremely wealthy popping up with a passion for AC traction (or me winning the euromillions) I cannot see how APT-P could ever turn a wheel in anger again. Just restoring the existing cars to running order would be very costly never mind all the additions and modifications needed to pass current requirements to allow it run as it should on the mainline.