Urgent investigation ordered into power outage that closed Heathrow Airport

Energy Secretary Ed Miliband has ordered the National Energy System Operator (NESO) to "urgently investigate" the power outage caused by a substation fire that shut Heathrow Airport on Friday.

The investigation by the body that operates Britains electricity grid would build a "clear picture of the circumstances surrounding this incident" and the UKs "energy resilience more broadly" to prevent it "from ever happening again", the Department for Energy Security and Net Zero said.

"We are determined to properly understand what happened and what lessons need to be learned," Miliband said.

The fire at the North Hyde substation in west London that supplies power to the airport led to thousands of cancelled flights and stranded passengers across the world.

Miliband said he has commissioned the investigation to "understand any wider lessons to be learned on energy resilience for critical national infrastructure, both now and in the future".

NESO is expected to report to the power regulator Ofgem and the Department for Energy Security and Net Zero in six weeks with its initial findings.

Heathrow closed in the early hours of Friday morning after the fire.

The Met Police has said that counter-terrorism officers were "leading inquiries" but are not treating the incident as suspicious.

Nearly 1,400 flights were disrupted by the closure, according to air traffic website flightradar24.com. Around 120 flights were diverted elsewhere.

Heathrow Airport said it was "open and fully operational" on Saturday morning, but the chaos has raised questions about the resilience of the major transport hub.

Fifty slots were added to Saturdays schedule to facilitate an extra 10,000 passengers travelling through it, the airport said.

On Saturday, more than 30 flights due to depart from the airport were cancelled and more than 15 were delayed, according to Heathrows live departure board.

It also showed that more than 70 flights expected to arrive at the airport had been cancelled, including from Doha, Riyadh, Dubai, Manchester, and Newcastle Upon Tyne.

One affected passenger is Ann Palmer, who said she was trying to get back to Aberdeen in Scotland with her husband but was "stuck" in Toronto, Canada, after their flight was cancelled on Thursday night.

She told the BBC that their onward flight from Heathrow to Edinburgh had been rescheduled for Monday but that they had received "no updates" from British Airways on their flight from Toronto to Heathrow.

The 64-year-old said BA had put them up in a hotel near Toronto Pearson International Airport and received vouchers for food and drink three times a day.

In Miami, Charlotte and her family were on heading to Heathrow on Thursday night when their aeroplane was "turned around mid-flight", she said.

"I have been stranded in Miami with my infant one year-old and three year-old son since then," she told the BBC.

"We have been passed around from hotel to hotel and American Airlines dont seem to care that we have an infant and a toddler in our party," she added.

The BBC has contacted BA and American Airlines for comment.

Substations are designed to produce, convert, and distribute electricity at suitable voltage levels. Heathrow uses three electricity substations, each with a backup.

There are also backup diesel generators, and uninterruptible battery-powered supplies which provide enough power to keep safety critical systems such as aircraft landing systems running.

However, when the fire broke out the substation, it was out of action, along with its backup.

Heathrows main fall-back was the two remaining substations, but the airports CEO, Thomas Woldbye, told the BBC that it "takes time" to "switch them".

He said the incident was "not created at Heathrow Airport, it was created outside the airport and we had to deal with the consequences".

In a statement released on Saturday evening, Mr Woldbye welcomed the investigation, saying that "we will support every effort to understand the causes and impacts of yesterdays off-airport incident".