Dukes got into a lot of trouble with the authorities over Tacho's etc... Montgomeries took them over eventually or i think they just acquired the trucks, as at one point between 2001-2002 you would see Montgomery truck pulling old dukes trailers and vice versa.
Here is a photo of an EX dukes unit in Montgomeries livery
http://www.flickr.com/photos/3867894...-9SwS6C-bE2vsH