The new T Charge arrives next week in London. It will quite rightly penalise my Golf. I'll have to pay £10 to drive into the central London congestion charge zone, in addition to the standard charge.

But no-one is stopping me from driving round my built-up area of south-east London.

Meanwhile the Skoda, as a Euro 4 car, will not be penalised by the T Charge.

But the next big change, the Ultra Low Emission Zone due to come into force in London in 2019, will penalise Euro 4 cars and older.

At the same time it will permit the Euro 6 diesels like the Nissan Qashqai N-Connecta DCI CVT to pump out NOx at 18 times the European limit.

It all seems very arbitrary.

Some cities - Oxford and Paris - have set ambitious targets on banning all combustion engines.

Problem sorted?

Not according to Prof Frank Kelly, the man whose lecture helped change my dad's mind. Even electric vehicles produce particulates from wear on brake discs and tyres, and by throwing up dust on roads.

In any case it seems unlikely that petrol and diesel vehicles will vanish in the next five or 10 years.

In which case there's a desperate need to sort the wheat from the chaff, the Tiguans from the Qashqais.

In a bid to do this the Mayor of London’s website is now going to publish Emissions Analytics’ Equa Index on its website.

When I phone my Dad to discuss the results, he's magnanimous in victory and agrees to accept a half rather than a pint because of the Skoda's higher particulates.

He says he is pleasantly surprised by the Skoda's NOx levels. But it's not enough. “I'm going to get rid of it,” he says.

It's partly because it's getting old. But he's also done some soul searching.

He worries about the particulates and the NOx in the city, so hopes to find a buyer who lives in a rural area.

His next car?