On the media yesterday (sorry source forgotten) they estimate there are a million vehicles being driven round without insurance, and that is not bicycles.
I have heard similar estimates.
Consider also the widespread misuse of red diesel fuel, and the number of vehicles without road tax.
And those who evade payment of congestion charges etc.
Time in my view for a crackdown. In most cases the vehicle should be impounded, and destroyed if unroadworthy or worth less than £1,000.
Unless there are strong extenuating circumstances, driving without insurance or road tax should result in a years driving ban.