A temperature record was broken in Britain on Wednesday as temperatures soared to 36.7C at Heathrow Airport.
As Wimbledon recorded the hottest day in its history, roads melted and rail services were disrupted, the Met Office said the previous record of 36.5C set nine years ago in Surrey had been broken.
The London Ambulance Service said it had seen call-outs to people fainting increase by more than a third (35%) compared to the same day last week, and a 28% hike in the number of calls it has received over the same period.
There were delays on the trains as Network Rail placed speed restrictions on some lines, fearing the metal tracks could buckle under the searing heat.
AA, the motoring group, said it had been called out to reports of road surfaces melting in the heat, bringing disruption to drivers.
London’s 36.7C record made the city hotter than Mediterranean hotspots including Barcelona, Ibiza and Athens.
Bottled water was handed out to lorry drivers stuck in the heat in huge tailbacks on the M20 in Kent, caused by striking ferry workers who have closed the Port of Calais.
Water was also handed out to passengers at Greater Anglia stations, including Ipswich and Norwich, as health experts urged people to keep hydrated.
A spokesman for the AA said: “The AA are receiving anecdotal reports from patrols that show that in places the road surface is softening, but there are no widespread problems at the moment. But if this continues we could start to see that.
“There was a man who put the stand down on his motorbike and it sank into the tarmac. The roads are soft in places.
“We have been very, very busy today.”