Lots of demonisation of diesels lately, but as usual, hack journalism tars all diesels with the same brush.
DPF diesels are good, gets rid of almost all the soot, but NOx output is still high.
EU6 compliant diesels cut the NOx right down, much better.
Many direct injection petrol engines are now dirtier than up-to-date diesels. As these petrol engines become more diesel-like in the way they introduce fuel and combust it, they get more fuel efficient, but they also generate particulates of their own (finer particles that can get deeper into the lungs when breathed in), unless they employ direct and indirect injection. Benzene and Toluene present in far greater quantities in petrol than diesel are some of the nastiest chemicals you can be exposed to (carcinogens) on a daily basis.
A well maintained and up-to-date car whether it be petrol or diesel will be infinitely cleaner than an old and badly maintained example.
Hopefully the people that draw up transport policy will see past the sensationalisation of "dirty" diesels and treat modern versions fairly. If the government is serious about cleaning up the roads it will get the filthy ancient taxis off the roads and have the bus companies retrofit tech to minimise particulate emissions.