These photos show how London's familiar landmarks disappeared under a grey blanket of smog as a "perfect storm" of pollution hit the UK.
The high pollution levels are the result of an unusual combination of factors, including a mix of local and European emissions, coupled with dust blowing in from the Sahara.
The City of London can barely be made out thanks to high pollution levels caused by local and European emissions, coupled with the dust blowing in from the SaharaAFPThe Canary Wharf financial district is dimly outlined through the smog blanketing LondonGettyA "view" of the O2 ArenaGettyTourists wear face masks in London to protect themselves from the air pollutionReutersA woman wearing an anti-pollution mask rides a bicycle at Hyde Park CornerGettyThe Orbit Tower in the Olympic Park should offer spectacular views across London when it reopens on Saturday. But not todayGetty
