The temperature in the shade at Heathrow airport, just west of London, hit 37.9 Celsius (100.2 Fahrenheit) in the mid afternoon, the Met Office, Britain's government meteorological bureau, told AFP.

"It's official. It is a record day in British weather history," a spokesman said. Earlier in the day the previous record high of 37.1 degrees Celsius (98.8 Fahrenheit), set in central England in 1990, was beaten, also at Heathrow.

Millions of Britons have been flocking to beaches, lakes and parks in recent days as the country has been blanketed under the heat wave currently affecting much of Europe.

However the 100-degree heat will chill the hearts of the nation's bookmakers, who now face potential payouts in the million of pounds (euros, dollars) after heavy betting that the mark would be reached.

Workers at London Zoo were also facing a busy day to keep species used to more temperate climes from getting too hot and bothered.

"We are regularly hosing down the sloth bears and the pygmy hippos, who seem to really enjoy it," spokeswoman Debbie Curtis told AFP.

"The primates are getting frozen fruit and nuts, like a giant ice lolly. The penguins are getting the same, but made from fish."

Pub and bar owners were also enjoying a special treat -- an extra three million pints of beer are expected to be drunk this weekend as Britons quench their thirst, according to estimates.

The hot weather has been experienced throughout much of the country, with Scotland edging close to its own record temperature, a slightly more modest 32.8 Celsius (91.0 Fahrenheit) seen in 1908.

In Birmingham, central England, the weather took a nastier turn when 15 people were injured by a lightning strike at a football match.

One woman suffered a heart attack as the lightning bolt struck a pitch where an amateur game was taking place during a heavy storm, ambulance staff said.

British temperature statistics go back to the mid-1870s, when a standardised global system for shielding measuring equipment from the sun was first introduced.

Met Office forecaster Roger White said he and fellow "weather nerds" were thrilled to see the 100-degree mark beaten.

"We tend to get fairly excited about these things because that's what interests us, that's why we joined," he said.

"It's an honour to be working on such a day."

TERRA.WIRE