National Grid has said it will “learn the lessons” after nearly one million people across England and Wales lost power on Friday.

But director of operations Duncan Burt told the BBC that its systems “worked well” after the “incredibly rare event” of two power stations disconnecting.

He said he did not believe that a cyber-attack or unpredictable wind power generation was to blame.

Regulator Ofgem has demanded an “urgent detailed report” into what went wrong.

It said it could take enforcement action, including a fine, after train passengers were stranded, traffic lights failed to work and thousands of homes lost power during the blackout.

An energy department spokesperson said National Grid must “urgently review” what happened.

National Grid power was restored by 17:40 BST on Friday but some train services continued to be disrupted on Saturday.

• ‘We were stuck on a train with no food or toilets’
• Why the power cut caused so much disruption
• Major power failure affects homes and transport

The power cut happened at about 17:00 BST on Friday, National Grid said, with blackouts across the midlands, the south east, south west, north west and north east of England, and Wales.

National Grid said its systems were not to blame.

Industry experts said a gas-fired power station at Little Barford, Bedfordshire, failed at 16:58 followed, two minutes later, by the Hornsea offshore wind farm disconnecting from the grid.

Speaking on BBC Radio 4’s Today programme, Mr Burt acknowledged the “immense disruption” the blackout had caused.

He said the near-simultaneous loss of two generators was more than the grid was routinely prepared for, prompting automatic safety systems to shut off power to some places.

“We think that worked well; we think the safety protection systems across the industry, on generators and on the network, worked well to secure and keep the grid safe, to make sure that we preserved power to the vast proportion of the country,” he said.

But he said the industry needed to examine whether these safety systems were set up correctly to have “minimal impact” on people’s daily lives.

RWE, owner of the Little Barford power station, said it shut down temporarily on Friday as a routine response to a technical issue, and called for National Grid and Ofgem to investigate the “wider system issues”.

And Orsted, the owner of the Hornsea offshore wind farm, said automatic systems on Hornsea One “significantly reduced” power around the same time others failed.

A spokesperson added: “We are investigating the cause, working closely with National Grid System Operator, which balances the UK’s electricity system.”

Police were called to help travellers during the huge disruption on the railways on Friday, with delayed passengers stranded for hours.

Disruption continued into Saturday for some routes.

• London North Eastern Railway, which runs between King’s Cross and the north of England and Scotland, said services were returning to normal, but a small number of trains were cancelled
• Great Northern services are still facing disruption and passengers are being advised to check their train’s status before travelling

• Thameslink services have returned to normal.

Govia Thameslink Railway (GTR), which operates Thameslink, Southern, Great Northern and Gatwick Express, says it is investigating why the power cut had such a severe effect on its trains.

Thameslink trains were particularly badly impacted as GTR had to deploy technicians to manually restart trains north of London.

David Hunter, energy analyst at Schneider Electric, told the BBC the grid was “pretty safe and pretty reliable”, but this was a “wake-up call” to the energy industry and businesses with critical infrastructure.

He said it was possible the transition to clean energy might be creating “greater stresses” on the system because energy such as wind power was less effective as a “shock absorber” to shifts in supply and demand.

Shadow business and energy secretary Rebecca Long Bailey said the impact of the power cut was “unacceptable” at a time when National Grid reported £1.8bn in profits and increased dividends to shareholders.

King’s Cross was one of the worst-hit stations, with all trains suspended for several hours.

Passenger Dayna McAlpine told BBC Radio 5 Live her train took nearly 13 hours to reach London King’s Cross from Edinburgh – a journey which would normally take less than five hours.

“By hour seven things were starting to get pretty tense,” she said. “People were threatening to self-evacuate off the train… Food ran out about five hours ago.”

Others on social media reported having travelled for 12 hours, while some rail passengers were stuck on trains until the early hours of the morning.

At the worst point of the power cut, about 500,000 people were affected in Western Power Distribution’s area – including 44,500 customers in Wales – while 110,000 Northern Powergrid customers also lost power.

In London and the South East, 300,000 people were affected, UK Power Networks said, and another 26,000 customers were without power in the North West.

Northern Powergrid said the problems had affected Newcastle airport and city’s metro system.

BBC Radio 5 Live listener Ed, in Woodford Green, north-east London, said he felt “totally cut off” as mobile phone networks were also down.

“You heard all the alarms going off all around. Everything else was pretty eerie and quiet,” he said. “There was no way we could know anything – it could be any reason that the power had gone down.”

At Ipswich Hospital, a back-up generator which was supposed to supply power to outpatient areas did not work after the power cut, causing problems for 15 minutes before power was restored.

How did the power cuts affect you? Email your stories to haveyoursay@bbc.co.uk

Please include a contact number if you are willing to speak to a BBC journalist. You can also contact us in the following ways:

• WhatsApp: +44 7756 165803
• Tweet: @BBC_HaveYourSay
• Send pictures/video to yourpics@bbc.co.uk
• Upload your pictures / video here
• Text an SMS or MMS to 61124 or +44 7624 800 100
• Please read our terms of use and privacy policy