Britain paid the highest price on record for electricity in London last week as the capital narrowly avoided a blackout, it has been learned.

National Grid’s Electricity System Operator (ESO) was forced to pay Belgium £9,724.54 per megawatt hour, more than 5,000% more than the usual price, last Wednesday to avoid a blackout. electricity in south-east London, as first reported by Bloomberg.

A sequence of problems around the hottest days on record in the UK has caused extreme stress in the electricity system and increased demand.

Temperatures topped 40C in the UK last Tuesday and firefighters in London reported their busiest day since World War II as the heatwave sparked hundreds of blazes across the city.

Rising power demand across Europe combined with a bottleneck in the grid has forced the ESO to buy power from Belgium at the highest price Britain has ever had paid to maintain the current.

Other factors, including scheduled outages for overhead line maintenance and a storm in Belgium impacting solar power, strained the system.

While the amount bought at the record amount was minimal – apparently enough to supply eight homes for a year – it revealed the UK’s reliance on importing electricity from overseas interconnectors, in particular the France, Belgium and the Netherlands.

A National Grid ESO spokesman said while another generation was available on Wednesday, power outages over the summer period meant a specific circuit was needed to get electricity to the right place.

National Grid ESO said: “We were bidding in a tight market and market prices were high that day because Europe also wanted power.

“We managed the system and kept the electricity going southeast.”

National Grid, which manages the UK’s infrastructure, added that although it plans to strengthen networks across the UK, importing electricity from abroad has cost advantages for consumers.

But Wednesday’s exorbitant transaction could be felt by households in their next energy bills, with energy suppliers passing on the costs.