When I drove trucks for the army, we often used to cart bits of bridges around the countryside for the engineers to play meccano with.
On a particular long and boring excursion, finding a lump of chalk, I duly gave the army truck white wall tyres. Still bored, I chalked "H.M. Queen & Sons" on one side, and "Stop me and build one" on the other.
The colonel at the bridging site didn't approve!