It seems some of the problems on the east coast line may be easing very slightly:

A train has left King’s Cross station headed for Peterborough. It was the first to leave since all services were halted earlier today.

The train departed platform one at around 9.30pm despite no signage alerting passengers to the departure.

Some were able to force their way through closed barriers to get onto the train. A staff member told other people waiting more trains might leave for Peterborough tonight but said she had “no idea” if services would run to other destinations.

The National Grid has offered a little more detail on what, exactly, went wrong today. A spokesperson has said:

This evening, we had an unexpected and unusual event, the loss of two generators that connect to the GB transmission system, which led to a fall in the frequency of the electricity system.

Even though these events are outside of our control, we have plans in place to respond and the system operated as planned by disconnecting an isolated portion of electricity demand.

We appreciate the inconvenience caused but this action allows the system to protect itself and limit the fall in frequency, allowing for power to be quickly restored. By 6.30pm, all demand was restored by the distribution network operators. The system is operating normally.

There will be no more Thameslink or Great Northern services running north of London for the rest of the day, the operator says. The Govia Thameslink chief executive, Patrick Verwer, says:

I understand this has been a very difficult evening for our customers and our staff. We continue to re-energise trains stopped in platforms but this will take considerable time which is why, despite our best endeavours, we are not able to run services north of London on the Thameslink and Great Northern routes for the rest of the day.

Our priority is to look after our customers. We have put on as many buses as we can source, arranged for our tickets to be accepted by other transport providers and organised taxis wherever possible. Details are available on our website and nationalrail.co.uk. Passengers with tickets will be able to use these for travel tomorrow and Sunday.

Prof Keith Bell, expert in electronic and electrical engineering at the University of Strathclyde has echoed Martin’s comments (see 8.13pm), saying the power cut was similar to an outage 11 years ago.

It seems to have been a very similar event to one in Britain in May 2008. However, this time we were kind of unlucky in that it was a deeper drop in frequency so more demand was tripped, and it happened during rush hour.

It’s fair to say that from a transmission system point of view, things have now been returned to normal, but the relays still tripped on the distribution networks.

One likes to think that, with the green light from National Grid that things are OK at the transmission level, they can restore supplies pretty quickly.

But how good have they been at managing the flow of information to ordinary people and, in particular, managers of facilities such as railway power supplies?

In the interests of transparency, Prof Bell declares his interests: “I hold the Scottish Power Chair in Smart Grids at the University of Strathclyde. (Scottish Power sponsors the Chair, not me. I speak as an independent academic. I have had various research projects over the years with the electricity companies, but only on the condition that results are published and, from my point of view, with the aim helping to improve engineering practice. I have also done work with government and Ofgem).”

CNN’s Eliza Mackintosh has tweeted evidence of the frustration some rail passengers are feeling this evening:

National Rail is stressing the scale of the problems at St Pancras:

Alastair Martin, the chief strategy officer of the energy solutions specialist Flexitricty, said the UK energy system “hasn’t seen anything like this for at least a decade”.

A similar energy system failure took place in May 2008 after the Sizewell B nuclear power plant tripped offline, two minutes before an outage at the Longannet coal-fired power plant.

“It was a coincidence, but it was dramatic,” he said. The twin outages also caused frequency to drop below the critical 50 Hz limit, which caused an automatic shutdown of parts of the energy grid, he added.

What is interesting this time around is that the energy system recovered far quicker than it did then. National Grid is more prepared, and it has more tools to help restore the frequency of the grid when it is struggling with inertia.

Footage has emerged of passengers being evacuated from a train in north London, which the operator says was travelling from Moorgate station.

Govia Thameslink Railway’s chief executive, Patrick Verwer, has said:

The wide-scale failure of the power grid that has brought our Thameslink and many of our Great Northern trains to a stand north of London continues to cause major disruption.

Despite our very best endeavours, we will not be able to run trains between London and Bedford, Cambridge and Peterborough and therefore advise customers they will not be able to travel on these routes for the rest of the day.

Where possible, we are advising people to use alternative routes and our tickets are being accepted by other transport providers.

The trains have been affected to the point where they require a technician to restart them and we are evacuating some of the trains that are stranded outside platforms. Our advice to customers is to stay on board trains for their own safety.

At St Pancras station, the Guardian’s correspondents have found a chaotic scene. Henry McDonald reports that commuters are taking matters into their own hands and starting to organise taxis to different destinations. They’re clubbing together in large numbers to go to Watford, St Albans and Boreham Wood, he reports.

One of them is the Guardian’s own Nicola Davis, who reports having had to share a ride northwards to Hertfordshire after hours of waiting for information, having only made it as far as Finsbury Park station.

At Kings Cross, Zoe Hebblethwaite, a 23-year-old legal secretary from Pontefract in West Yorkshire, has described the situation as “absolute mayhem”. The 23-year-old has been stuck for hours, having arrived at the station at 5.30pm before being told to leave until further notice.

They have closed doors of the station – no power whatsoever. Outside Kings Cross station is absolute mayhem nobody knows anything nobody can find an assistant to speak to at this point. No commuters are allowed in... There is so much confusion.

Thomas Edward, a consultant at the energy specialist Cornwall Insight, says Little Barford tripped offline at 4.50pm and may have triggered the automatic shutdown of the windfarm.

The key thing about today is that it is very windy. The strength of the system is determined by how many power plants you have running all at once. If there are a lot of power plants running and one has an outage, then the others can pick up the slack.

Windfarms don’t have the same level of stability as a power plant. So, on a windy day when we rely more on wind power thermal power plants, it is more difficult to manage. We need to know exactly what happened from National Grid and the network operators to understand the full cause of the blackout.

We’ve just had an updated statement from National Grid Electricity System Operator:

Just before 5pm this afternoon, we saw a loss of supply from two separate power generators causing loss of power in selected UK areas. The issue is now resolved and the system has returned to normal.

Our initial analysis indicates that system defences worked as expected during what was an unusual event. Anyone continuing to experience a local issue should contact their local Distribution Network Operator for assistance.

Mitchell Collier, from Rayleigh, Essex, was planning on travelling to Newcastle with friends. He said: “It’s awful. We’re going on a boys’ weekend to Newcastle to watch the football and obviously we can’t get there at the moment. There’s been no updates from the train company, they’ve just kind of shut the doors on us, just kicked us out.”

He added that the only information he and his friends were getting was from Twitter and the Trainline app. He said: “We’ll potentially have to cancel the whole trip. That’s the money gone, though, hotel and all that.”

Michael Ajibowu was trying to get home to Biggleswade in Bedfordshire. He said: “I’ve just come from Finsbury Park. I was stuck there for about an hour. I thought I’d come down to central London for better access. When I got here the doors were locked.”

• This entry was amended on 13 August 2019 because Biggleswade is in Bedfordshire, not Hertfordshire as an earlier version said.

Philippa Higgins was travelling to York when the power cut hit King’s Cross. She was evacuated along with hundreds of passengers.

She said: “There was overcrowding so they kicked us out. The guy who shut the door got yelled at but it’s not his fault. There has been no information and I’m just scrolling Twitter.”

While it’s hard to be precise about how many people have been affected, especially once commuters are taken into account, PA Media estimates that there are close to a million customers facing blackouts, with 500,000 people affected in the Midlands, the south-west and Wales, and another 300,000 in London and the south-east.

A spokeswoman for Northern Powergrid, which serves Yorkshire and the north-east, said 110,000 of its customers lost power, while Electricity North West said at least 26,000 people were without power in the north-west of England.

Newcastle airport was also plunged into darkness by the power cut. Scott McKenzie was travelling through Newcastle airport when the power cut out for around 15 minutes, in what he was told by officials was “due to a wider problem in the region”.

“It was a bit worrying to start – more so because various alarms were going off and staff clearly didn’t quite know what was going on either,” the 31-year-old from Cardiff told PA Media. “Some of the spaces in the airport have little daylight – we were literally plunged into darkness and people were using their phones as torches to see and get around.”

My colleague Fran Lawther is at King’s Cross station in London, where she took this picture of passengers streaming out having been asked to leave. LNER tweeted that people should not attempt to travel to or from the station.

Stockport was one of a number of areas to lose power earlier this afternoon, although it has now been restored. In Cheshire police said they were aware of a power outage in the Ellesmere Port area, including in Great Sutton and Little Sutton. Engineers are thought to be working remotely to restore the power. Meanwhile, in Bradford several sets of traffic lights stopped working.

One Twitter user said that it was “like GTA out here” with “every car and pedestrian for themselves!”

A spokesperson for Electricity NorthWest said: “We have experienced multiple power cuts across the region, this was due to a fault with National Grid. Power should now be restored, however if you continue to experience issues with your supply or need any support please contact us on 105.”

The National Grid blamed issues with two power generators causing a loss of power in different areas across the country. Hundreds of thousands of customers have been affected.

Many social media users posted images of difficulties they had been facing as they travelled. One Twitter user posted this video of people climbing the steps in silence at Clapham Junction:

A large-scale power cut left swathes of the UK without electricity and caused major disruption to transport networks. While the National Grid said that the issue had been resolved by early Friday evening, knock-on effects for commuters appeared set to continue, with significant rail cancellations and passengers being advised to stay at home.

Follow our live coverage for details of how services in your area are being affected. Here’s our current news story on the situation.