Are there Catalytic converters on busses?

Cats have been fitted to diesel engines in the European market for at least 20 years. I had a 1994 Vauxhall with the Isuzu diesel, that ws fitted with a cat. As for the Dennis, it's difficult to say. You need to actually remove the inspection hatches to take a good look at the exhaust system. Whilst it may not have been fitted when new, someone may have retrofitted the cat and related electronics in order for it to stay within emissions regulations for an inner city area. If you know where it has worked in the past, could you not research the relevant authorities emissions legislation to find out the minimum standard for a 29 seat bus in thaty area? I have a friend who has a Gardner engined truck which he is not able to use near London, but it's ok for the rest of the country.