In principle, and as an IAM member, I find the idea of higher speed limits for drivers who have passed an appropriate advanced driving test to be appealing. However, unless/until we have cars that require a personalised key and biometrics to drive (at which point they will be self-driving and this discussion will be moot), there would appear to be significant hurdles to effective and efficient enforcement of such a scheme.
I realise that this is apples to oranges, as "push bikes" don't have VRMs or RK's and therefore are harder to monetise enforcement of, but the availability of exempt electrically assisted pushbikes has resulted in a vast number of illegal electric motorcycles that are indistinguishable from the legal assisted pushbikes (until they whizz past you at 40mph, uphill, without peddling, at night without lights, or any other legal or safety requirement). Riding a conventional mostly road legal motorcycle with a small number plate, you stand a fair chance of getting pulled for your crime. Riding a completely illegal electric motorcycle that looks like a road legal assisted bike (there are probably at least 2 in the country that are road legal), chances of getting pulled are next to zero.
If some drivers are allowed to do 100mph, and a car is observed doing 96, how do you ascertain whether the driver of that vehicle on that occasion is allowed to do 100? Not as a one off, but as widespread enforcement. There are many, many potential ways to do this, some far less flawed than others.
edit: Obviously we are all missing the real point - the country's richest Roland Rat impersonator needs to do or say something to appeal to the man in the street who voted Tory last time after Labour told him (as a key part of their election campaign) that he voted for Brexit because he was variously stupid and/or racist.