Network reconfigured with SSEN Distribution to restore all customers including Heathrow

National Grid said power supplies had been restored to all customers connected to its North Hyde substation in West London, including Heathrow, after a fire at the site damaged equipment and cut supplies. In an update timed at 2pm on 21 March 2025, the operator said it had reconfigured the network in partnership with the local network operator SSEN Distribution to restore all impacted customers and to resupply the parts of Heathrow connected to North Hyde.

The fire was reported by National Grid in an update at 5.30am on 21 March 2025. By 7am the same day, the operator said power had been restored to 62,000 customers as of 0600, with 4,900 still without power, and that it was working alongside SSEN, the distribution network operator for the area, to reconnect affected domestic customers. The 2pm update described the reconfiguration as an interim solution while further work is carried out at North Hyde to return the substation and the network to normal operation.

At 6am on 22 March 2025, National Grid said supplies had been restored to all customers connected to the substation, including Heathrow, allowing operations to resume at the airport, and that it was implementing measures to help further improve the resilience levels of its network. Later that day it welcomed the National Energy System Operator's investigation into the power loss.

Why it matters for households

The incident shows how a single substation fire can interrupt supply to tens of thousands of homes and to a major airport at the same time. National Grid's figures indicate that most of the 66,900 customers affected at the 0600 snapshot on 21 March had supply back within hours, with 4,900 still off at that point; the later updates say all customers connected to North Hyde were restored. The restoration for Heathrow and other customers connected to the substation was described as an interim arrangement while work continues to return the substation and network to normal operation, so the network is not yet back to its usual configuration. National Grid said it was working with the Government, Heathrow and the police to understand the cause, and that it was implementing measures to improve the resilience of its network. It has not been reported what those measures involve or when they will be completed. The guide to how Britain's electricity network is run explains the roles of transmission and distribution operators; the power cuts hub covers what happens when supplies fail.

What happens next

The National Energy System Operator is investigating the power loss, and National Grid said it welcomes the investigation and will work closely with all parties to understand the cause. National Grid said further work at North Hyde is needed to return the substation and its network to normal operation. No date has been given for completing that work or the investigation.