Prince Charles and the Duchess of Cornwall have landed in a city where the smog is so bad it’s been called a “poisonous gas chamber”.
The couple’s travels plans to Delhi in India have had to be amended because of the pollution in the city.
The smog is so bad here that medics say breathing the air is equivalent to “smoking 50 cigarettes per day”.
The air quality index - on which anything over 100 is considered unhealthy - hit the severe level of 451 - and in parts of the city some monitors even recorded levels off the scale - over 999.
The RAF plane which flew Charles and Camilla from Penang in Malaysia had to take on extra fuel in case it was unable to land.
Pilots need a minimum level of visibility in order to see the runway on approach and during the flight the Prince was told that visibility at the airport had been as bad as zero at one point.
The smog has been caused by a combinations of factors; Colder air and slow, moist winds, crop burning on farms, fires and fireworks to celebrate the festival of Diwali and Delhi’s notoriously heavy traffic.
Prince Charles and Camilla arrived on a day when schools have been closed to protect childrens’ health.
Construction activity might also be forced to stop until pollution levels recede.
And the city’s half-marathon faces being cancelled to prevent what medics fear could be a “health emergency”.
Doctors say in the long run, these conditions will increase the risk of lung cancer.
A change in wind direction is likely to make things worse.
A northwesterly wind will bring toxic fumes from neighbouring states where farmers have been burning crop stubble before the new planting season.