Colin
For too many people I'm afraid idiocy is an aspiration rather than an affliction.
In circumstances like these the law always puts the responsibility onto the potential miscreant not to transgress. For example, the offence never was a failure to have a current tax disc - it was a failure to
display it. No amount of "it's in the post", "I forgot to fix it into the car", "the dog's eaten it", "I was abused as a child" etc can mitigate the fact that the damned thing wasn't where it was supposed to be. Similarly no-one was ever prosecuted for failing to post a tax return; the offence is failing to
render one (to the appropriate address). In neither case could there be any "excuse" - these are absolute offences. It's unfortunate that magistrates and judges seem to have been given powers to mitigate in certain offences when it comes to sentencing (BTW nice one, Oscar...

). That has set off the media in pursuit of "justice" whenever some crime is perceived as not entirely the fault of the person who committed it. Now the presumption is that this culpable third party should include government agencies for not reminding us of our own obligations. It's said that ignorance is no excuse for breaking the law. In that case why should stupidity or irresponsibility be treated with any more leniency?
Yes - DVLA does still send out road tax reminders - I had one just this week. Untaxed vehicles are by definition also uninsured, and so anyone who has an accident involving one of these is up a gumtree when it comes to redress - or at least a long way up a certain smelly creek with a very small paddle. As regards prosecuting those who run untaxed vehicles, it is surely not beyond the wit of man to produce from DVLA's database a list of cars which were taxed in the immediately preceding year but have no current tax or SORN declaration. This list could give names, addresses, postcodes, car reg numbers - in fact everything necessary for an authorised agency to identify and seize untaxed cars and prosecute their keepers. There's even a widely-used computer system called ANPR which will spot and flag up any of these cars as they pass by a roadside camera. How's
that for an absolute offence?
What's lacking is the will to do it.... Now that
IS the fault of government and its agencies. I think I'll write to The Times...
DM
PS Speaking as a former revenue officer I can only remind you of the cardinal rule of taxation: Heads I win; Tails you lose. (You can have that reminder on the house).