• A fire at a National Grid substation led to a major shutdown at Heathrow Airport in March.
• The fault responsible for the fire had been known since 2018, raising concerns about maintenance practices.
• The incident stranded thousands of passengers and caused over 1,350 flight cancellations.
• Ofgem has launched a formal investigation into National Grid for potentially breaching its maintenance obligations.
• Energy Secretary Ed Miliband described the findings as "deeply concerning".

A fire that caused significant disruption at Heathrow Airport on March 21 was attributed to a failure at a National Grid electricity substation, which had not been properly maintained. The investigation by the National Energy System Operator (Neso) revealed that a component failure significantly impacted Heathrow, the busiest airport in Europe. This incident resulted in the cancellation of over 1,350 flights and stranded approximately 300,000 passengers, raising critical questions regarding the resilience of Britain's infrastructure, according to Channel News Asia, Reuters, and BBC.

The root cause of the fire was identified as moisture ingress into a transformer bushing that National Grid had known about since 2018. However, maintenance actions to rectify this issue were deferred multiple times, according to findings from the investigation. Despite the prolonged inaction, Energy Secretary Ed Miliband deemed the scenario “deeply concerning,” reflective of a breakdown in oversight regarding critical infrastructure maintenance in the U.K., as noted by AA, BBC, and Reuters.

The disruption also affected external services, plunging 67,000 homes into darkness and causing delays in power restoration at Heathrow, which took several hours. Although local data centers managed to maintain operations using backup generators, the airport faced significant operational challenges, according to AA and BBC.

In light of the findings, the energy regulator Ofgem has initiated a formal investigation into National Grid's practices to ascertain if there was a breach of legal or licensing obligations regarding maintenance provisions. The analysis underlined failures in diagnosis and preventative action taken by National Grid, which has since pledged to re-evaluate its asset inspection and maintenance programs, as reported by Reuters, Channel News Asia, and AA.