London will be affected by smog

With temperatures set to reach as high as 26C (77F) on Wednesday, beating much of the Mediterranean, experts from Department of Environment, Food and Rural Affairs (Defra) have forecast increased ozone levels for London and the south-east.

People with breathing difficulties can be sensitive to ozone pollution and may experience some problems, a Defra statement said.

Ozone is produced when sunlight reacts with polluting gases created mainly by vehicle exhausts.

"Avoiding exercise outdoors in the afternoon can reduce exposure to ozone," Defra advises.

The dry and sunny weather is set to last until Friday with cooler weather predicted for the Easter holiday weekend, the Met Office has said.