"Roger Mills" gurgled happily, sounding much
like they were saying:

It would probably destroy the catalytic converter - just as it would
in a car with a petrol engine.

Never seen a diesel with a catalytic converter yet, apart from the odd
bus.

I must have been ripped off then. It cost me over £600 to replace the
catalytic converter on my 1999 Volvo V70 2.5D when it failed!

No, you were replaced over £600 to replace the particulate filter.