It has long been predicted that the tide will begin to turn against diesels over their local pollution issues, and it looks like London mayor Boris Johnson has fired the opening salvo with his announcement that pre-Euro6 emissions legislation diesels will be charged another £10 per day to enter London from 2020, if the proposal goes through consultation as expected.

I’ve got a couple of big concerns over this that the RV setters and other industry figures we spoke to didn’t seem unduly concerned about, which surprised me, to be honest.

Firstly, until September 2015, it will be possible for fleets to take on Euro5 diesels, which could, if run on a four-year basis, be defleeted towards the end of 2019 – right before Boris’s proposed additional charge is due to arrive. So I can see there being a big desirability gap between Euro5 and Euro6 models. And it would be naïve to think it’s just a London issue, with a number of other UK cities all some distance away from meeting their air quality targets and therefore at risk of EU fines.

Then there’s the issue of diesels becoming less appealing to the public. I know of several people who moved to diesels as private purchases, seduced by the fuel economy when the mileage they do doesn’t justify the extra cost. These people will see the headlines and are likely to move away from diesel, even though there’s no more rational argument to at this stage.

There’s already a discrepancy between the demand for new diesel fleet cars and the amount of used buyers that want them three or four years down the line. Branding diesels as dirty killers of inner-city kids isn’t going to help that.