In the past five years, Essex police have had to pay out 222 times for repairs caused by its drivers putting petrol in diesel engines or vice versa.

To combat the problem, the force has fitted large yellow flaps over the filling point, reminding the drivers which fuel to use.

The vehicles have also been fitted with voice reminders telling drivers “this is a diesel vehicle” when the fuel cap is opened, while they have begun fitting devices which fit into the filler neck making it almost impossible to get a petrol nozzle into a diesel tank.