Heathrow Airport is believed to have had enough power to avoid completely shutting down on Friday as a substation fire blazed two miles away.
National Grid chief John Pettigrew has since said that two other substations were fully functional and could have provided an adequate amount of power to keep the airport open.
The revelation has followed a weekend where officials and politicians scrambled to pinpoint blame for the monumental shutdown of Europe's largest airport - leading to around affected 200,000 individuals as more than 1,300 flights were cancelled.
Energy secretary Ed Miliband has also since flagged his concern with the national resilience of the UK's infrastructure.
PA
Pettigrew explained that two extra substations are "always available for the distribution network companies and Heathrow".
He added: "Losing a substation is a unique event – but there were two others available. So that is a level of resilience."
“I can’t remember a transformer failing like this in my 30-plus years in [the] industry," the energy boss said.
More than 200,000 people were stranded on Friday as Europe's busiest airport shut down
PA