It is one year since the VW Dieselgate scandal broke. Up until 12 months ago, King Diesel's ascent to topple petrol from the car fuel throne in the UK looked relatively assured. Ever since Kyoto in 1997, the role of CO2 in global warming made it the prime enemy. And since diesel engines produce less CO2 than their petrol equivalents, European governments rushed to legislate in favour of the fuel.
But however planet friendly it may be, diesel produces other pollutants - particulates and oxides of nitrogen - which are increasingly being tagged as very bad for human health. Poor air quality in cities has become a major concern and the finger is pointed squarely at not-so-clean-any-more diesel.
Although the main effects of the emissions-test-cheating scandal on VW sales have been in the US - where VW's shenanigans perfectly illustrated that the gasoline-loving Americans were taking a lot of convincing that diesel was The Juice of Choice anyway - it's likely that diesel has now stalled here, too. Of the near 1.6 million new UK cars registered so far in 2016, just over 780,000 have been petrol powered, with diesel coming in second on 767,000 and AFVs (alternatively fuelled vehicles) increasing by 21% over 2015 to 51,394 new cars.
Manufacturers still have a great deal invested in diesel however and are not ready to write it all off just yet. When I met Rupert Stadler, the boss of Audi and part of the VW empire, in the thick of the scandal last autumn, I suggested that the crisis surely spelled the beginning of the end of the diesel. He was having none of it. 'I'm convinced the diesel engine is fantastic,' he protested. 'It has good torque, low fuel consumption and big range. Its CO2 emissions are 15% lower than of petrol engines of the same horsepower. This is the reason why 70% of our European customers buy that technology. They are happy with what they get.'
He has a point. Before one announces the death throes of diesel, it's worth recalling why it became so popular in the first place. The oil-burner is still the engine of choice for most long-distance road warriors. They are liked very much by out-of-town drivers who cover many miles with their foot down, the engine turning at barely over 2,000 rpm on the motorway without the frenetic revving you get with a petrol engine. Diesels haven't clattered like tractors for years and are almost inaudibly refined these days.
They are also inherently more efficient, turning more of the energy in the fuel into forward motion (it is this which accounts for the low fuel consumption and hence lower CO2 emissions of diesel cars). But those sooty particulates and toxic NOx gasses are its Achilles heel. In cities full of roads clogged with buses and lorries, pollution caused by diesel fuel has become dangerously high.
Legislation which led to their rise may well lead to their demise. Achieving the latest Euro 6 emissions standards has taken a lot of engineering know-how. The result is engines which are complex and expensive to make and repair. So the diesel may well have reached its apogee. Even Stadler seemed resigned to this.
'We agree together with other manufacturers that diesel is one of the answers to the very ambitious CO2 targets in Europe. But nevertheless we are investing huge sums on plug-in hybrids, which is a bridging technology towards fully electric cars. By 2018, we will have an SUV, which is fully electric with 500km of range. And we are able to bring fuel cells on the road.'
Coming of driving age during the era of low-cost airlines, I'd never done a seriously long European drive. And with our regrettable conscious uncoupling from our neighbours on 23 June, now seemed to be the best time to attempt one before it was too late.
Would it be possible to drive one of the most popular fleet vehicles all the way from London back to its place of origin in Munich on one tank of fuel? A BMW 320d ED (EfficientDynamics) to be exact, a big favourite among fleet buyers with its frugal 2-litre engine, tax- efficient emission CO2 rating of 109g/km and rock solid residuals. And in BMW's 100th year.
The ViaMichelin recommended route is 1,137km or 706 miles. It would be a close-run thing. Not least because in the brave new world of honest, real-life fuel consumption and conditions, the drive would be the first stage of the Gwyther family's annual summer trip to Le Marche in central Italy. Failure could prove a real-life horror show.
So no taped-up doors and bonnet to reduce drag. No - a boot full of juvenile clobber, even a telescope. Plus the growing Gwyther offspring in the back drawing down power from the engine on their iPads.
Neither, with all that 'he hit me first!' racket coming from the back, was I inclined to proceed gingerly, doing 56 mph all the way down the autoroutes and autobahns. Compared to the poorly repaired and jammed solid UK motorways, the French autoroutes heading south towards Reims, Nancy are billiard-table smooth and have hardly any cars on them. They cost, of course - tolls from London to Munich total EUR50.
But if any car stood a chance of making it in style and comfort, the 3 Series was it. And we were doing very well indeed. West of Strasbourg with getting on for 750km completed, I had well over a quarter of a tank of fuel left. My belief is I could have got all the way there. (One driver from a green driving website made it all the way from Essex to Milan with 79 miles of fuel left to spare. But, in an amazing act of self-discipline, she kept to 55.6 mph as she trundled down through Les Vosges in Alsace.)
The truth is I bottled it. Not fancying being a stranded loser on the hard shoulder in my day-glo yellow vest waiting for the German equivalent of the AA with a jerrycan of juice, I filled up before we went completely dry. (And, you can find diesel in France for just over EUR1.1 a litre, which before Brexit and the pound's nose-dive against the euro was pretty cheap.)
Later as we headed south into Switzerland, I passed several Teslas driven by well-heeled Swiss. Would I rather have been feeling pious in one of them? With electric vehicles, I still find myself consumed by 'range anxiety.' The AA man cannot turn up with a mini power station. The 3 Series by contrast, despite looking like a municipal rubbish tip, filled with Autogrill sandwich wrappers, odd Crocs and portable DVD players had become a cosy three-day home. It's a great set of wheels and far more civilised than the departure lounge at Stansted.
After our holiday when we returned to The Smoke, one of the first moves made by the new London mayor Sadiq Khan was to announce a ban on vehicles on Oxford Street - the totemic thoroughfare for unacceptable levels of diesel fume air pollution. Walking or cycling down Oxford Street does not smell too good - it's a sooty, noxious canyon.
In a funny way, driving across Europe in this car felt a bit like the trip to New York on a Boeing 747 - a small end of an era. We're not there yet, but it's heading one way. The next time I take a car to Italy, it may well have gone autonomous and I may not even be driving it myself.
Waiting for me on my return was an email from Nissan about petrol stations. Apparently more than 75% of those in the UK have closed in the last 40 years - 8,472 filling stations now, down from 37,539 in 1970. Assuming a steady rate of decline, Nissan predicts that by August 2020 there will be only 7,870 left.
Meanwhile the number of electric vehicle charging locations has increased from a few hundred in 2011 to more than 4,100 in 2016. But even assuming we all buy an electric car, the question of how we are going to generate all the electricity necessary to charge them up is another issue. Our new prime minister apparently feels a deep suspicion at the prospect of the Chinese building and controlling our new nuclear power stations. We're going to be filling up rather than plugging in for some time yet.