I think the market for used diesel cars will collapse over the next five years, with severe implications for anyone banking on current 'residual values'.

As well as city centre Nox bans, the cost of rectifying expensive failed emissions kit at 4-5 years old will finally sink in. So if you want to take advantage of fuel economy and low tax over a high mileage over three years, lease one. Don't buy one. And hope that the lease rates still reflect today's high residuals on diesels. Or get a petrol hybrid.