Why do most Keen Bros Trucks have a Volkswagen Beetle on the back?

The Beetle is not just there for cosmetic purposes although we think it looks good. If you look carefully at Herby you will see it is full of concrete. The reason being, is that the truck has to be loaded for you to do a driving test. We felt that the novelty of a Beetle looked better than plain drab concrete blocks. So poor old Herby now weighs about eight tons.