Heathrow Airport is considering taking legal action against National Grid after a report found the substation fire which caused the airport to shut down earlier this year was the result of a known fault.
Europe's busiest airport was brought to a standstill by a substation inferno, with thousands stranded, hundreds of flights cancelled, and over 100 nearby residents evacuated.
The power outage that followed left the airport closed for 18 hours, and cut power to thousands of households.
But the new report, ordered by Energy Secretary Ed Miliband, revealed that the fire could have been avoided, and that National Grid had known about the fault that likely caused it for over seven years.
Despite being made aware of the issue back in 2018, the electricity company let several opportunities to fix it go by.
The report points to two specific times National Grid missed the chances to prevent the failure.
The airport now plans to take legal action against the company, saying they expect National Grid to "carefully consider what steps they can take to ensure this isn't repeated."
National Grid "could and should" have prevented the fire, Heathrow told the BBC, and the airport expected it to "take accountability for those failings".
A Heathrow spokesperson previously said: "A combination of outdated regulation, inadequate safety mechanisms, and National Grid's failure to maintain its infrastructure led to this catastrophic power outage."
"Our own Review, led by former Cabinet Minister Ruth Kelly, identified key areas for improvement and work is already underway to implement all 28 recommendations," they added.
The report, released today, reveals expert opinion suggesting the fire at the North Hyde Substation "most likely" started after the failure of high-voltage bushing, which allowed moisture to enter the equipment.
This failure caused the fire which ultimately spread out of control, burning for several days before firefighters were able to extinguish it.
More than 67,000 were left without power after the fire at the substation back in March, and 270,000 journeys disrupted from the airport.
The government is now demanding urgent reforms and upgrades to the ancient grid system, some of which are already being pushed through by government in a bid to increase capacity as the UK moves towards Net Zero.
The first opportunity to avoid the outage came in 2018, when tests revealed a higher than expected level of moisture in oil samples.
The levels of moisture meant "an imminent fault and that the bushing should be replaced", the National Grid Electricity Transmission's relevant guidance said.
Basic maintenance to the substation that was required in 2022 was also subsequently deferred.
The report, released on Wednesday by the National Energy System Operator (NESO), noted that opportunities to mitigate the severity of the issue were "not actioned".
It also revealed the airport had become too reliant on a single source of power.
An initial report commissioned by Heathrow into the saga, led by former Transport Secretary, Ruth Kelly, found that the chief executive of Heathrow airport was asleep at home when the decision to shut the airport was taken.
Energy Secretary Ed Miliband called the NESO report "deeply concerning", because "known risks were not addressed by the National Grid Electricity Transmission.
Simon Calder: Heathrow reportedly had enough power to keep running despite 'unprecedented blaze'
Senior staff tried to wake Thomas Woldbye with calls and messages but he could not be reached.
But the report concluded that the decision to suspend flights was the right one, and was essential to protect safety and security of passengers.
An interim report from NESO, the National Energy Security Operator, said that the cause of the North Hyde Substation fire, remains unknown.
Government sources were confident there had not been a cyber attack at the time, but no cause has yet been determined.
The National Grid said there were “important lessons to be learned” about cross-sector resilience following the review into the North Hyde substation fire.
A National Grid spokesperson said: “As Neso’s report sets out, in Great Britain we have one of the most reliable networks in the world, and events of this nature are rare.
“National Grid has a comprehensive asset inspection and maintenance programme in place, and we have taken further action since the fire. This includes an end-to-end review of our oil sampling process and results, further enhancement of fire risk assessments at all operational sites and re-testing the resilience of substations that serve strategic infrastructure.
“We fully support the recommendations in the report and are committed to working with NESO and others to implement them. We will also cooperate closely with Ofgem’s investigation.
“There are important lessons to be learnt about cross-sector resilience and the need for increased coordination, and we look forward to working with government, regulators and industry partners to take these recommendations forward.”
