
Passengers have been forced to evacuate trains in south London as temperatures soared above 30C (86F).
A fault on a train near Loughborough Junction brought all services in the area to a halt, three of them outside station platforms, Thameslink and Network Rail said in a joint statement.
“Without power and air conditioning on such a hot day, we pulled all resources from across Sussex and Kent to get personnel on site to safely evacuate passengers as quickly as possible along the track,” it said.
They apologised to affected passengers for the “difficult and uncomfortable experience”.
The incident began at about 10:40 BST with the evacuations of the first two trains completed at about 12:20 and the third at about 13:10, a spokesperson said.
They added that due to engineering works, this was the only route taking Thameslink services south out of London and “and disruption is expected into the evening”.
The heatwave was forecast to bring temperatures of up to 33C (91F) to the capital on Saturday, and drew thousands to its lidos and bathing ponds to cool off.
But warnings over heat-related illnesses and remaining safe while swimming in open water have been issued as London Ambulance Service (LAS) predicted a surge in 999 calls.
Meanwhile, researchers at the London School of Hygiene and Tropical Medicine and Imperial College London (ICL) released a study that used historical data to forecast the capital could see 129 excess deaths related to this week’s hot temperatures.

Across England and Wales, excess deaths from Thursday to Sunday are estimated at about 570 people.
By lunchtime, the temperature at Heathrow Airport had reached 31C (88F).
Researchers said their assessment highlighted how extreme heat posed a growing threat to public health in the UK.
Dr Garyfallos Konstantinoudis, lecturer at the Grantham Institute at ICL, said: “Heatwaves are silent killers – people who lose their lives in them typically have pre-existing health conditions and rarely have heat listed as a contributing cause of death.
“This real-time analysis reveals the hidden toll of heatwaves and we want it to help raise the alarm.”
He added that heatwaves were an “underappreciated threat” in the UK.
Temperatures had been forecast to hit 32C (90F) across the south-east England on Saturday having already reached that level on Thursday in London.
The UK Health Security Agency issued an amber heat-health alert covering all of England to warn vulnerable populations of the health risks, including “a rise in deaths”.
LAS said on 13 June, when temperatures hit 28C (82F), it received 7,000 calls compared with 5,500 on a typically busy day.
The service has activated plans to manage high demand, including deploying community response cars, increasing clinicians for phone assessments, and speeding up patient handovers at hospitals.
Stuart Crichton, director of 999 operations at LAS, said: “We have been very busy this week and expect to be even busier this weekend as temperatures climb even further.
“We would will like to remind Londoners to only call 999 in a life-threatening emergency.”
He said that older people, the very young and those with pre-existing conditions are particularly vulnerable to heat-related issues.
“Look out for neighbours, family or friends who may need some help and make sure they are able to keep cool during the heat,” Mr Crichton added.
Dr Lorna Powell, an NHS urgent care doctor in east London, said: “We are seeing cases of heat-related illnesses rising in our urgent care departments.
“Heat exhaustion can quickly trigger more serious illnesses as dehydration sets in and the cardiovascular system becomes overwhelmed.”

Andrew Lewington, from London Fire Brigade, told the BBC that 15 people have died so far this year in the capital’s waterways.
He said there had been an increase of 15% in the number of callouts for water rescue, equating to 12 a week.
“People need to understand what lies beneath water and think twice about jumping in,” said Mr Lewington.