Has diesel had its day? With the news that four cities across the globe are banning diesel cars outright from their centres, the ongoing Volkswagen emissions furore, plus the added Fiat Chrysler accusations emerging in the US, and doctors calling for restrictions and fines on diesel cars here in the UK as a result of mounting evidence that they’re damaging our health, it seems increasingly likely.

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Good news, you might think – especially if you’re a car enthusiast, many of whom have always loathed diesel. Financially, though, the U-turn we may see is a big cause for concern, as it could set off a chain of events which would result in a price slump on the used car market that would affect many of Britain’s used car owners and buyers.

Already, six British cities have been given the go-ahead to create clean air zones in which drivers of diesel cars could face congestion charges. Ten more are being proposed. In London, a fee of £10 on top of the current congestion charge has been suggested.

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Were that to be repeated across the country – and that could be the case as soon as 2019 – it would mean around £200 a month added onto an average city-centre commute. Not exactly pocket change, in other words, and more than enough to provide a big incentive to swap into a petrol model, sharpish. Even those who don’t commute by car would probably avoid buying a diesel if they knew they couldn’t get into any large British city without paying a fee.

So far, there’s been no effect on the price of diesels, according to James Dower, the senior editor of Cap HPI’s Black Book. “It seems that consumer and fleet appetite for diesel vehicle has held up,” he says. “There is no waning in demand for diesel vehicles in the new or used market. Values have moved broadly in line with petrol engined equivalents through 2016, with little visible impact from negative headlines through the year.

“Used values for petrol and diesel vehicles have tracked in line with seasonal trends, and there is no evidence of a sudden drop in wholesale appetite or consumer demand. If pressure on values is coming, it’s some way off yet.”

Nevertheless, the question of whether to choose petrol or diesel is being raised more and more by car buyers in emails to motoring publications such as Autocar. The Volkswagen dieselgate scandal has potential diesel buyers feeling uneasy; the prospect of £200-a-month hike to their commuting costs will almost certainly do far more damage.