St Paul's Cathedral stands shrouded in smog as seen from Primrose Hill in London on April 3
Smog has reached alarming levels in many parts of London and South of the UK. That famous London skyline is now all covered up behind a sheet of smog.
Experts are saying it's a mix of dust from the Sahara and air pollutants from continental Europe. Emergency services have come under strain because many people are calling the emergency helpline number and school children remaining indoors. From the South, experts are now warning the smog will affect the north too in the coming days - reaching as far as Wales.
The government has been passing the blame on to Europe, but many residents are sceptical. "I don't think there is correct information. All we are told that there is a bit of dust from the Sahara... and bit of pollution coming form London. And also European countries like France. And then there is dust from the Sahara. The combination of the two is creating the smog. But you know, where is the truth? What is fact and what is fiction, we don't know," Jive Weathery, an actor, told NDTV in London.
But many experts have confirmed that fine dust from a continent away - from the Sahara too - has been picked up by global wind systems.
Whatever is the cause of the smog, many Londoners with asthma have been finding it hard to cope.
"I have had a asthma attack today. I haven't had one in years so just had to sit down, take the puffer," said Cory Miller, a resident of London.
The Prime Minister may have had to miss his morning jog, but it was his government that was on its toes trying to defend its record on controlling air pollution.