You already need to reapply for your license every 3 yrs after 70. You need to inform DVLA or relevant medical conditions. I don't think your GP is normally consulted if you tell them you are in good health, but if your GP (or other doctor) has told you not to drive and you do, or has advised you to inform DVLA about a medical condition and you don't you will be breaking the law.
Whilst there is anecdotal evidence of dotary old drivers there seems to be little evidence that they are causing or involved in lots of accidents.
We will all be old one day - and whilst I don't object to simple measures to make life genuinely safer for all, complex steps which bring little benefit and significant cost aren't really a good idea.
Given that there is a good chance a significant proportion of people here will be working until they are 70 - suddenly treating them as on the scrap heap at retirement probably isn't a good idea.
I'm sure in many cases where someone is driving and the shouldn't be there are family who are aware and who could if they wished intervene. I'm sure GPs don't really want to spend their time filling in DVLA forms.
The police have the equipment to identify who is driving without insurance. With a bit of ficus and effort...
no the police have the ability to spot vehicles which have NO insurance, not to identify easily if the person behind the wheel is actually insured on that vehicle.
A much better option would be what the Aussies do. Your 'car tax' also includes 3rd party cover.
I don't see how that is a better system. You can't purchase Vehicle Excise Duty (tax disk) in the UK without proving you currently have Insurance in place for somebody to drive the vehicle. In the UK system the cost of insurance is paid by those with the highest actuarial risk, presumably in Oz everyone pays the same - so "safe, responsible" drivers are subsidising the reckless? Uninsured vehicles just become untaxed vehicles in an Oz based system. There could be an argument for aligning expiry dates of Insurance, VED and MoTs but it does mean you are loading all the cost at one time which will disadvantage the poorest.