Two months ago my car broke down and needed to be towed home by the RAC. My local Ford dealer diagnosed the problem as a blown spark plug which had disintegrated and damaged the forth cylinder, requiring a replacement engine at £3200.

The car is two years old and has a three year warranty; however, Ford is refusing to replace the engine under warranty as the car had its third service at 35,700 miles at an independent garage, which didn’t replace the spark plugs.

I find it hard to believe that a spark plug can cause this much damage. If a spark plug were to blow I would expect a drop in performance, not such damage that then requires a brand new engine. Have you come across anything like this before?