Sir – I have some agreement with Roger Keable (Letters, December 31), but I would like to add better still, that if the Government was truly concerned about carbon emissions from cars, that is apart from an excuse to charge extra tax revenue, they should be encouraging research, or conversion of say cars built in the last six to eight years to run more efficiently.

I feel that there is little technical difference in recent engines and those built within the last few years that a simple retune (rechip maybe) is all that is really needed.

Then these cars could be reclassified to a lower road tax band. Pious hope I feel.

Martyn F Fawcett, Kidlington