The NHS in South West London has issued a pollution and pollen alert for today - Thursday

The combined effect is likely to cause breathing issues for the vulnerable at a time when hospitals are already struggling to cope with the impact of a junior doctors strike.

The organisation said: "Pollen and pollution levels are very high today & hospitals are currently very busy.

"If you have to go outside, stay in the shade, especially between 11am and 3pm, and avoid exercise or activity that makes you hotter."

It added: "We're seeing high numbers of people coming in with breathing difficulties and older people who are dehydrated.

"If you, or your child, has asthma or other respiratory conditions – keep taking your regular preventer inhaler and stay indoors wherever possible, keeping windows and doors closed as much as possible. If you do need to go outside, shower and change your clothes to wash pollen off.

"Older people are particularly at risk of becoming unwell during a heatwave. Drinking water and staying out of the sun are most important for staying well."