Reduced fuel duty for diesel came in in 2001 (25yrs ago) and was removed following the scandal of manufacturers cheating the emissions tests in 2015 (11 yrs ago)

We've known diesel emissions are bad for health for a long time and ULEZ schemes improve people's health, particularly children https://www.bbc.co.uk/news/articles/c1l1r1zne1ro

But some selfish people still think it's their right to drive highly polluting vehicles and let everyone else bear the cost

ULEZ / LEZ zones are a good thing