Why aren't fuel pumps designed so that nozzles can't be replaced wrongly?

Can anyone confirm that all petrol nozzles at a fuel station will also fit in the diesel holder of the pump? Around eight months ago I filled up at a supermarket with £60 of what I thought was diesel. It was in fact petrol, and the mistake cost me close to £500. I never went back to the fuel station until yesterday. I know exactly the pump that I used. It was definitely marked diesel but what I think had happened was that a previous user, possibly on purpose, had swapped the nozzles. So yesterday I temporarily did the same to see if a petrol pistol can fit a diesel pump holder and vice versa. It was clear that they are interchangeable. Has anyone else come across this and why are the nozzles not different so that this mistake cannot occur?

Asked on 22 August 2010 by alandisney

Answered by Honest John
They won't fit in a modern Ford Fiesta, Focus, Mondeo, S-Max or Galaxy with Easyfuel. They will fit in everything else that has not been modified with a misfuel-prevention device.
Similar questions
I filled up with Shell V power at my local filling station today. Previously I have never been able to get more than 42 litres of fuel in, today it took 49 litres and still hadn't shut off. I have a 62...
I thought I would try Shell V-Power diesel. At a Shell Garage I saw a logo in red with a V-Power sign on it and filled up from the pump showing the red V sign. This was the only one on the forecourt....
I have just bought a 9 month old third generation Honda Jazz SE. The manual recommends the use of 95RON super unleaded petrol. Will I damage the engine if I use ordinary unleaded?