I think it's a really tricky issue which needs to be given more air time personally!
It has, to be fair given a lot of "air time" on here, possibly one of the most thread starters I've seen.
Depriving someone of their car so; their independence, the ability to go to the shops, see friends, go to social events and all the rest is a big step when for maybe 50 years having a car is a bit like having a right arm, you'd miss it if it went after 50 years.
You can "grass them up" (as we say round here) to the DVLA or impersonally or via the doctors, but the issues is if they still have the car and the keys then they'll just keep driving, be it with an invalid licence and probably invalid insurance as they've failed to disclose.
You can disable the car, take it away for repairs and it never comes back, no parts or whatever and you know what a new car costs...You could ask the local police to come and tell him he can't drive any longer (if they have any time to spare) any number of things really.
Ultimately anyone with AZ lives in their own world and if you're telling something that they see as "wrong" then they simply don't believe you.
I've seen this topic so many times but each person has to handle it in the way that works for them. I don't want to share the roads with someone with AZ and you can't go a week in the papers where some "elderly person" hasn't smashed through the window of a shop or a worse.
Probably this an issue that need addressing but how would you frame the law?
K