The tax is absolutely correct in my view.
It's quite surprising at how many folk express surprise considering the CO2 differential tax policy has been around for a number of years.
We hear about poor families, frankly poor families could not afford to run a large car in CO2 terms post 2001. The truth is real poor families run much older cars if they can afford to own one at all.
The policy is correct but I think it smells of a stealth tax when it is retroactive.
I think the tax should apply to changes in car ownership rather like the Council Tax banding can change if the are home improvements which change the banding but only to the new owner.