This “shocking” photo shows London covered in a filthy layer of black smog as unusually high levels of air pollution hit the capital.
The picture, taken by IT worker Pete Buckney at the top of Horniman Hill in south London, shows a stark contrast between the darkness blanketing the city and the blue sky above.
Air pollution was more than double the usual level for the capital on Thursday, according to the London Air Quality Network.
It came as temperatures plummeted below freezing amid clear skies and low wind levels.
Dr Gary Fuller, of King’s College London’s Environmental Research Group, explained: “On cold days you get a cold layer of air that sits close to the ground and all of our air pollution is put into that layer, therefore the concentration goes up.
“Yesterday was one of those rare moments where air pollution was actually visible; you can’t normally see it like that.”