This article is more than 1 year old

This article is more than 1 year old

The government has announced an inquiry into the power cut on Friday that left people stuck in trains for up to nine hours and almost a million people in England and Wales without electricity.

The outage, the biggest in a decade, caused chaos during the evening rush hour, plunging Newcastle airport into darkness and causing gridlock in some areas as traffic lights stopped working.

Describing the disruption as “enormous”, the business secretary, Andrea Leadsom, said: “National Grid must urgently review and report to Ofgem. I will also be commissioning the government’s energy emergencies executive committee to consider the incident.”

The energy watchdog, Ofgem, had already demanded an “urgent detailed report” from the National Grid to better understand what went wrong, and threatened enforcement action.

National Grid, which runs the electricity transmission system, said the power cut was caused by the “rare and unusual” simultaneous loss of two large generators. Little Barford gas-fired power station, in Bedfordshire, and then Hornsea offshore windfarm, off the coast of Yorkshire, are believed to have become disconnected from the grid.

Manuel Cortes, the general secretary of the TSSA transport union, said that with the prospect of a no-deal Brexit “it’s reasonable to wonder if this is a foretaste of things to come. Along with an economy sliding towards recession and expected food shortages, we now seem to be a country where blackouts happen without warning, travel grinds to a halt, traffic lights stop working and – terrifyingly – hospitals are left without power.”

He added: “Boris Johnson can’t remain silent over this – he must quickly provide answers and illumination.”

Play Video 1:14 Power cuts spark transport chaos in London - video

A backup generator at Ipswich hospital which was supposed to supply power to outpatient areas did not work as expected, but East Suffolk and North Essex NHS foundation trust said “patients were kept safe and cared for throughout” the 15-minute period before power was restored.

About 300,000 UK Power Networks customers were affected in London and the south-east of England, a spokeswoman said, and Western Power Distribution said an estimated 500,000 people were affected in the Midlands, south-west England and Wales, with power restored to them all shortly after 6pm.

Rebecca Long-Bailey, the shadow business and energy secretary, said: “Disruption on this scale is unacceptable.

“National Grid – which in May posted £1.8bn in profits and increased dividend payouts to shareholders – must urgently provide a full account of what went wrong, and why.”

In a statement, National Grid said it was very pleased the government inquiry had been ordered as it would help understanding of the causes of Friday’s power cut and why it had such a significant impact.

It said the Electricity System Operator (ESO), a legally separate business within the National Grid Group, responsible for balancing supply and demand, was carrying out its own inquiry.

A National Grid spokesperson said: “In the meantime the ESO has already initiated its own internal review of the response and is collaborating closely with Ofgem, local distribution networks and affected power stations/generators to understand the causes.”