A massive fire near Heathrow Airport caused widespread chaos for travellers as a major power outage forced the closure of one of the UK's busiest transport hubs.

The blaze at a nearby electrical substation triggered severe delays across London's transport network.

London Heathrow announced it would remain closed for the entire day following the fire at the electrical substation.

Security experts have called for urgent investigation into whether Russia could be behind the blaze that has wreaked havoc for thousands of travellers.

The Metropolitan Police stated there was "currently no indication of foul play" but stressed that it would "retain an open mind".

It comes amid growing concerns about the vulnerability of critical infrastructure.

Downing Street has said there were "questions to answer" regarding how a single fire had been able to shut down Heathrow completely.