'OLD 6'66 is an old bus owned by the Luxton & District Traction Company's. The bus often has engine troubles and breaks down and is not considered to be safe on the roads (according to Stan). The bus resembles a London double-decker bus, only painted green instead of red.
The bus is not popular amongst the staff and seems to only be used as a replacement service like in "No Smoke Without Fire" when Blakey ordered Stan & Jack to use it when the no.11 had a broken wheel bearing. The bus is not in good condition in the episode as its engine started bursting out smoke, then stalling before finally catching fire. The fire spread all over the bus until it was completely destroyed. It is unknown what happened to the bus after this but it is most likely it got scrapped.
OLD 666 is a former London Transport (later London Country) RTL-type