They can monitor "Genuine" mileage through the MOT.
Down side means they wont know the details for the 1st 3 years. So they will simply just relay on drivers honestly.
I suspect that this what will happen at some point. Shortly after your MOT you'll get your tax bill in the post.

Or more likely the tax you owe will pop up on your Digital Starmercard ID account and the cash will be taken automatically from your bank account. No ifs. No buts.
And if you haven't got the cash in your bank your EV will be remotely disabled until you can pony up, along with a deposit for next year. Plus interest of course.


