An expansion of Heathrow Airport may have averted Friday’s power meltdown, it has emerged.

For more than two decades, the airport has been campaigning for approval to expand.

Yet since the airport’s first public call to add a runway in 2003, the plans have been restarted and stalled on numerous occasions.

Now documents uncovered by The Telegraph suggest an expansion may have prevented the energy meltdown caused by a fire at a substation on Thursday night that led to the disruption of more than 1,300 flights.

This is because plans for an expanded site have previously mooted the idea of an additional power supply at the airport.

These are just three electricity substations, or “grid supply points”, which supply the airport and they cannot replace each other without lengthy reconfiguration.

A 2014 report by Jacobs, a global planning and infrastructure consultancy, found that the “key weakness” to the electric supply for the airport was “the main transmission line connections to the airport”.

The authors added: “It is not unreasonable to assume that the expansion of the airport would be accompanied with additional provision of resilient supplies and back-up generation or uninterruptable power suppliers to serve the additional services.”