Ownership of the Whitney Bridge confers certain tax privilages. There is an ongoing cat and mouse game going on between the successive owners and the Inland Revenue. Some have tried to claim that the tax free zone extended beyond bridge revenues.
The bridge was on the market again in 2002.
http://www.igreens.org.uk/whitney_toll_bridge.htm
I remember chucking a 2p in the box as a kid to get my bike across.