Heathrow Airport bosses have hit back at claims made by the chief executive of National Grid who say the airprort had enough power from other substations despite Friday's shutdown.

A huge fire at the electricity substation in Hayes on Thursday evening caused severe delays at the airport resulting in more than 200,000 air passengers having their flights to or from Heathrow cancelled or diverted on Friday, March 21 after the airport was closed all day due to the fire.

John Pettigrew from National Grid told the Financial Times there were two other substations "always available for the distribution network companies and Heathrow to take power". He added: "There was no lack of capacity from the substations. Each substation individually can provide enough power to Heathrow. Losing a substation is a unique event - but there were two others available. So that is a level of resilience."

In response to the comments, a Heathrow Airport spokesperson said: "As the National Grid's chief executive, John Pettigrew, noted, he has never seen a transformer failure like this in his 30 years in the industry. His view confirms that this was an unprecedented incident and that it would not have been possible for Heathrow to operate uninterrupted.

"Hundreds of critical systems across the airport were required to be safely powered down and then safely and systematically rebooted. Given Heathrow's size and operational complexity, safely restarting operations after a disruption of this magnitude was a significant challenge," reports Sky News. 

Initially Metropolitan Police counter-terrorism officers led the investigation but the force said the fire is not believed to be suspicious so the London Fire Brigade is now leading the probe.

It comes after a report by consultancy firm Jacobs highlighted in November 2014 how electricity outages could shut down Heathrow. The report, published on a Government website, warned: "Even a brief interruption to electricity supplies could have a long-lasting impact as systems can take time to recover."

The document stated "outages could cause disruption to passenger, baggage and aircraft handling functions", and "could require closure of areas of affected terminals or potentially the entire airport."

In its appraisal of operational risk at the airport, Jacobs said provision of on-site generation and other measures to ensure resilient supply appeared "to be adequate" to enable Heathrow "to withstand and recover from interruptions to supply". It added that the airport operated "within risk parameters that are not excessive or unusual for an airport of its type".

Energy secretary Ed Miliband has commissioned an urgent investigation into the power cut.

Money expert Martin Lewis has explained your rights to get compensation if your flight is affected by the Heathrow chaos. Martin explained that the exact amount you get depends on the distance the flight travelled and the amount of time it was delayed, as long as it left a UK or EU airport, as long as the airline was to blame for the delay.

Find out more about how to claim compensation by clicking here.