Based on true events . . .
An elderly married couple, Eric and Daphne, travel to France in their old banger for a weeks touring. Within hours of arrival, their car is rear-ended by Ahmed, the driver of a sleek Mercedes.
As it's his fault, Ahmed persuades the couple to take his vehicle for the week, while he has theirs repaired. The couple reluctantly agree.
Good for his word, Ahmed has mechanics fix the vehicle and respray it. He also supervises the concealment of four kilos of heroin into the cars bodywork.
Holiday over, Eric and Daphne retrieve their vehicle a week later and set off home.
A fortnight later and whilst mowing his lawn at home in Surrey, Eric is approached by a man of middle eastern appearance. The stranger explains that the car sitting on the couples drive is exactly what his wife seeks. They agree an inflated fee and watch the stranger drive off.
Later that evening, the couple decide how to spend their profits from the illegal contraband.