John Wright ) gurgled happily, sounding much like
they were saying :

But they are required by law to be fitted to new cars sold after
1992 IIRC.

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.

Not quite - a cat was specifically legislated to be fitted to all new
petrol cars, and that was what killed "proper" lean-burn, as the cat is
based upon 14:1 air:fuel - requiring the use of the lambda sensor to keep
it there.

The MOT doesn't *specifically* require the fitment of a cat, but the
emission requirements would be very difficult (at least) to meet without
one.