When I was a young un I bought a Daimler Sovereign which was a brilliant but thirsty car. After owning it for a couple of weeks I foolishly got caught out between services and ran out of Petrol and was stranded on the A6.
Anyhoo I managed to find a 'phone box and called out the AA, after about an hour the mechanic arrived, stroked his chin a little and then reached inside and flicked a switch, and within a few turns of the key the engine burst into life.
The mechanic looked at me and said "you didn't know that these have twin fuel tanks then?" I had to admit that I didn't.
He continued "The fuel filler caps either side of the car didn't give it away then No?"