I'm a shameless petrolhead, with a dilemma

I freely admit to a lifelong passion for motor cars, starting with my father's splendid battleship gray 1949 Rover 14 convertible - why, oh why did he sell it? - and my first car, a beige Morris Minor 1000, 1961 model.

I've come a long way since then, another Morris Minor, a sporty Triumph Herald convertible, various MGB roadsters, a Ford Cortina, a Volvo and then a long love affair with the BMW marque, which endures to this day.

So what's my problem? Well, like many British motorists, we followed the government and the motor industry's fiscal incentives to buy diesel-powered cars. More robust, more kilometers per liter, and according to the advice at the time, less polluting than petrol engines.