Hundreds of Eurotunnel passengers face having to abandon their travel plans as the UK prepares for 'Furnace Friday'.
The Cross-Channel rail operator said it had taken the "unprecedented decision to cancel daytrip/overnight tickets" for travel tomorrow after the extreme temperatures buckled air conditioning units on the trains.
Several carriages had to be taken out of service on Thursday due to the suffocating heat, causing five-and-a-half hour queues, and forecasters have warned that Friday could be even hotter.
It came as the MCC broke its strict dress code and said it would allow members to enter the pavilion at Lords Cricket Ground without a jacket for the first time in its history.
The announcement was made as England became became the hottest country in Europe as temperatures soared to 36C leading to widespread cancellations of summer outdoor events.
A spokesman for Lords said: "To our knowledge this is the first time members have been given prior permission not to bring a jacket at all.
"Before, once or twice a season, they would be given permission to move around the pavilion without a jacket if it got really hot. It is the first time it has been prior agreed that they don't even need to bring a jacket with them."
The ongoing heatwave, which could break all time records on Friday if conditions pass 38.5C, has already led to fun runs, charity walks, dog shows, gigs and fairs being called off over fears that participants would overheat.
And as large numbers of stargazers were expected to gather tonight to the lunar eclipse, which could see the Moon turn a deep burgundy red from around 9pm, firefighters called for a ban on barbecues in parks in case sparks set light to parched grass.
Highways England also urged motorists to avoid throwing litter from cars to prevent glass starting fires on motorway verges.
Many dog shows were called off after The Dogs Trust warned animals would suffer if they exerted themselves in the heat, while councils cancelled sports days and the National Trust abandoned some outdoor events.
Gymkhanas and summer horse shows all over Britain were called off because the ground is too hard leading to fears riders could break bones if they fell from the saddle.
Hospitals were forced to cancel non-urgent operations as A&E departments were flooded with people complaining of respiratory problems and dehydration. Nurses reported feeling exhausted, sick and dizzy as temperatures soared inside hospitals
Saffron Cordery of NHS Providers said: "Some trusts are reporting record numbers of people coming in to A & E. This extra activity is leading to delays for patients requiring planned operations such as knee and hip replacements.
"The extreme heat has also highlighted the shortcomings of ageing buildings which are not designed or equipped to deal with these conditions."
Britain's transport infrastructure also struggled to cope in the heat, with train passengers on LNER forced to plug in their own fans after air conditioning broke. Rail services across the country were cancelled as tracks buckled leading to speed restrictions.
Temperatures of 37C were recorded by commuters on the London Underground, and commuters in the capital were also forced to endure high air pollution, leading to major Sadiq Khan issuing a major alert.
The RAC said it is expecting breakdowns across the UK to be up around 15-20 per cent on what they would normally expect for late July by the end of Thursday.
However although the hot weather is expected to cost the country in excess of £1 billion in lost productivity, Britain's seaside resorts were experiencing a boom.
Southend-on-Sea has seen the biggest growth with train bookings to the town for July and August up an 210 per cent compared to the same period in 2016 while bookings to Margate have increased by 164 per cent, St Ives, 79 per cent and Scarborough 76 per cent.
Professor Sam Fankhauser, director at the Grantham Research Institute, at the London School of Economics said: "There is no doubt some industries will be hit hard by the heatwave and we usually see productivity drops of around 8 per cent when the temperature goes above 30C. For industries like construction which are outside that could be up to 30 per cent.
"But it will probably be a boom for people who are selling ice-cream or who have outdoor business."
The heatwave was forecast to end with thunderstorms on Friday with yellow weather warnings issued for the north and east. The Met Office said there were risks of torrential downpours, flooding, gusts and hail.
However although the weekend will feel cooler, the hot weather is expected to return next week.