Why are the classic compatible trains not tilting? Are they too expensive to build for minimal time gains?
HS2 Ltd (ie DfT) are besotted by the 400km/h design speed of HS2, and have written that into the train spec.
This was when there were supposed to be separate captive and classic-compatible fleets.
Now there are only going to be CC trains, at least before HS2b, they are even more insistent on having the high speed capability.
I'm fairly sure the fastest current tilting trains are rated at 250km/h (155mph) - Talgo's trains do that in Spain and elsewhere.
There is a speed penalty to pay (weight, suspension) for the tilt capability, and restrictions on gauge too, like the Pendolino.
However, Alstom has said they can design a faster tilting train, but it is not in production.
But of course it will not be tilting at that speed, only at 125mph (or possibly 140mph) on the WCML, non-tilt on HS2.
All this says non-tilt HS2 trains will pay the penalty for running on the WCML north of Lichfield/Crewe/Golborne (10-15 minutes slower to Glasgow).
The West Coast Partnership is supposed to integrate WCML and HS2 planning and operation, so we'll have to see what happens when HS2 Ltd meets Joseph Locke.
Somehow, like IEP, I suspect the DfT consultants' vision will prevail over what a mere TOC might think.
NR is in the middle of this; they are looking at possible WCML upgrades to avoid some of the tilt penalty.