With London and the South East under a level 3 heatwave alert a senior doctor has warned people to take steps to avoid heat-stroke.

With the heatwave due to continue into next week Dr Martin Stockwell, joint medical director at Epsom and St Helier University Hospitals NHS Trust, said: "During weather like this, our A&E teams often see an increase in the number of people suffering from sunburn, heat exhaustion and dehydration.

"We would urge anyone spending time outdoors, and especially those preparing for fun-runs, marathons or any outdoor sporting event in the sun, to take extra care, wear at least 15+ sun lotion, ideally a hat, and drink plenty of fluids.

"It’s vital people look after themselves in this heat."

Heat exhaustion is a collection of symptoms brought on as the body struggles to control its temperature and can develop into heat-stroke.

Dr Stockwell said, "If someone with heat exhaustion continues to be exposed to high temperatures, the more serious and life-threatening condition of heat-stroke may develop and the body can become dangerously dehydrated.

"Our cooling mechanisms, such as sweating, stop working and our temperature starts to rise."

To avoid getting too hot have plenty of cold drinks, avoid excess alcohol caffeine and hot drinks; reduce sunlight coming through windows and keep windows open at night but closed if the room is cooler than outside.

The body cools itself down by sweating and if the body loses too much liquid or salt then the symptoms of heat exhaustion develop.

For more information on staying safe in hot weather visit www.nhs.uk.