Great Britain's grid operator paid about £10 million to fire up gas power plants to avoid a rare summer power supply crunch on Wednesday evening as extreme heat put pressure on the energy system. This was reported by Qazaqyia.kz citing The Guardian.

On Wednesday, Neso paid more than four times the usual daily average to secure enough electricity to balance the power system after it issued a notice late on Tuesday asking generators to provide extra electricity to meet rising demand due to the heatwave.

The warning was cancelled on Wednesday afternoon after the operator agreed to pay about £1,400 a megawatt-hour, nearly 20 times the average electricity market price in June last year, to secure about 1.7 gigawatts of imported electricity from the continent.

A Neso spokesperson said: "This is due to the impact of extremely high temperatures affecting Great Britain and the continent, and low wind."

The government-owned body added that the electricity supply was not at risk and that the decision to issue a margin notice did not mean a blackout was imminent.

Neso – which manages the energy systems in England, Scotland and Wales – had warned on Tuesday evening it would need an extra 1,900MW of power to avoid falling short of the electricity required to power homes and businesses within its normal safety margins on Wednesday evening.

The notice in effect called on Britain's electricity generators to provide any extra power they could from their plants.

It is more common for Neso to issue such notices during particularly cold spells in winter, when there is more demand for heating. But demand for electricity is expected to climb between 7pm and 10pm on Wednesday as people turn on electric fans and air conditioning units to try to keep cool.

Electricity prices have risen sharply across European markets in recent days as the heatwave has gripped much of the continent, pushing demand higher and causing a string of power plant outages.

On Tuesday evening, a handful of Great Britain's gas power plants were paid almost £4m to generate electricity for just a few hours as millions of sweltering viewers turned to air conditioning, fans and icy drinks during England's second World Cup game.

An area of high pressure has trapped heat across the region and slowed wind speeds, which has knocked renewable energy generation. There has also been lower output at some nuclear plants in France, where high river water temperatures are making it more difficult to cool the reactors.

The combination of rising electricity demand and falling generation across Europe has pushed market prices to multiyear highs.

The UK broke its all-time temperature record for June on Wednesday, with 35.8C recorded in West Sussex, England.

The sweltering heat is expected to strain the UK's infrastructure. Train operators have urged passengers to travel only if necessary on Wednesday and Thursday, schools have been closed across southern England and Wales and hospital appointments have been cancelled.

Several trade unions, including the Trades Union Congress, the Bakers, Food and Allied Workers Union and the Fire Brigades Union, have called for workers to take part in a strike on the hottest day.

There is no maximum legal temperature for workplaces in the UK, although there is a minimum legal temperature of 16C in offices.