I am totally mystified as to how my diesel Ford Mondeo got contaminated with petrol. Last week I filled up with diesel at my local supermarket and drove a round trip of 200 miles without a problem. I again filled the car – at the same supermarket – with diesel and, after leaving the car at home for a few days, drove 150 miles. At the end of the journey the car died and I was towed to my local garage, who found petrol in the tank.

The car has done around 150,000 miles and a couple of weeks prior to this I had all four injectors replaced along with the fuel pump filter, which was clean. I have contacted the supermarket who have told me that they have not had any problems from any other drivers and suggest contamination can occur in an old car because dirt accruing over time. This avoids the fact petrol has been found in the car and I had the system checked before replacing the injectors.

I have fuel receipts that prove I bought diesel at the supermarket and I am considering legal action. Can you offer any advice?