"Dave Plowman (News)" wrote
John Wright wrote:
No - it's simply the emissions regs were tightened then which means in
practice a cat is needed.

They were tightened so that only a cat equipped engine would pass -
thus ending research in the UK into Lean Burn engines which would not
pass the emissions regulations at that time.

If there was a possibility of them passing after more development, why
would this stop if they had other benefits?

It didn't stop development. Diesels are lean burn.

Though it is an oddity of the regs that, rather than having blanket
regulations for particular classes of vehicle, that it distinguished
between different fuel types.

Oh, and LB can't meet the NOx regulations specified for petrol engines.