• Hottest July day with 36.7C recorded at Heathrow
• Hottest day in Britain since 2006
• Urgent health warnings issued
•Train cancellations and slow-downs
• Wimbledon reduces capacity in roaring heat
• UK hotter than Barcelona and Athens
Urgent health warnings have been issued and commuters warned to expect delays as Britain sweets through its hottest July day ever recorded.
The Met Office tweeted just before 3:30pm it had recorded 36.7C (98F) at Heathrow.
Young children, the elderly and those with serious illnesses are at particular risk amid fears the hot weather could lead to hospitalisations and even deaths.
On the transport network, speed restrictions have been imposed by Network Rail on some train lines amid fears the metal tracks could buckle under the searing heat.
Virgin has cancelled 20 trains because of the rocketing temperatures as commuters brace themselves for what is predicted to be a chaotic rush hour this evening.
London Heatwave
(01 of10)
Open Image ModalLONDON, ENGLAND - JUNE 30: People cool off in a fountain outside the Southbank Centre on June 30, 2015 in London, England. The UK is currently experiencing a heatwave, with temperatures of 35 degree celsius forecast tomorrow in some parts of the country. The extreme heat has already seen train cancellations and a health warning has been issued. (Photo by Rob Stothard/Getty Images) (credit:Rob Stothard via Getty Images)
(02 of10)
Open Image ModalWoman reads her book by The Serpentine, in Hyde Park, on June 30. (credit:John Stillwell/PA Wire)
(03 of10)
Open Image ModalPeople cool off in part of the Princess Diana Memorial Fountain in Hyde Park, London, on June 30. (credit:John Stillwell/PA Wire)
(04 of10)
Open Image Modal (credit:John Stillwell/PA Wire)
(05 of10)
Open Image ModalPeople cool off in a fountain outside the Southbank Centre on June 30, 2015 in London, England. (credit:Rob Stothard via Getty Images)
(06 of10)
Open Image Modal (credit:NIKLAS HALLE'N via Getty Images)
(07 of10)
Open Image ModalLONDON, ENGLAND - JUNE 30: Spectators enjoy the hot weather during day two of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 30, 2015 in London, England. (Photo by Carl Court/Getty Images) (credit:Carl Court via Getty Images)
(08 of10)
Open Image ModalA group of teenagers play in a water fountain in central London on June 30, 2015. Temperatures soared above 40 degrees (104 degrees Fahrenheit) in Spain and Portugal on Monday prompting health concerns and the scorching heat was expected to move north to France and Britain later in the week. AFP PHOTO / NIKLAS HALLE'N (Photo credit should read NIKLAS HALLE'N/AFP/Getty Images) (credit:NIKLAS HALLE'N via Getty Images)
(09 of10)
Open Image ModalTwo women enjoy the afternoon sunshine on the banks of the river Thames at low tide near the south bank centre in London on June 29, 2015. Britain is set for a heatwave over the coming days as temperatures could rise to as high as 35 degree centigrade.AFP PHOTO / NIKLAS HALLE'N (Photo credit should read NIKLAS HALLE'N/AFP/Getty Images) (credit:NIKLAS HALLE'N via Getty Images)
(10 of10)
Open Image ModalA man sunbathes beside the River Thames in central London on June 30, 2015. Temperatures soared above 40 degrees (104 degrees Fahrenheit) in Spain and Portugal on Monday prompting health concerns and the scorching heat was expected to move north to France and Britain later in the week. AFP PHOTO / NIKLAS HALLE'N (Photo credit should read NIKLAS HALLE'N/AFP/Getty Images) (credit:NIKLAS HALLE'N via Getty Images)