London mayor Sadiq Khan today felt the full impact of the toxic air crisis in the Indian capital Delhi.
The mayor, who suffers from asthma, braved polluted streets on the third day of his Asian trade mission.
The India-Sri Lanka test match was repeatedly interrupted on Sunday because of fears for the health of players.
The World Health Organisation recently ranked Delhi the most polluted global city.
The mayor joined children at a school where pupils are taught to recognise dangerous pollution levels.
He also announced a trial of new air sensors in London which could monitor up to a thousand hotspots near schools and hospitals.
Air pollution is a global problem that harms the lives of millions of people. We hope to work with key cities across the world and in India, including with our good friends here in Delhi.