However, the Jacobs report, titled Operational Risk: Ground Infrastructure Heathrow Airport, stated: “Beyond the management of supply and grid services, which lie outside the airport’s control, the responsibility for managing electricity supply risk lies with the airport and businesses operating from the airport.

“While some services can be temporarily supported with generator or battery back-ups, the key weakness is the main transmission line connections to the airport.”

It warned: “Outages could cause disruption to passengers, baggage and aircraft handling functions and could require closure of areas of affected terminals and potentially the entire airport.

“Even a brief interruption to electricity supplies could have a long-lasting impact as systems can take time to recover.”

The fire destroyed a vital transformer at the North Hyde substation and also a back-up transformer, rendering the substation inoperable.

The airport is also served by two other substations powering different areas. However, in order for these to run the entire airport, the power supply to all the terminals needs to be re-engineered.

While this is happening, Heathrow relies on its back-up supply, which is not sufficient to run the entire airport.