Fire alarm 'briefly impacted airfield operation'

The glitch came after the airport was beset by complications arising from a fire alarm at the airport’s air traffic control tower at around 4.30pm.

While staff were evacuated and the situation assessed, some inbound flights had to be diverted to other airports. Outbound passengers, meanwhile, were left waiting in terminals.

Heathrow confirmed in a statement the alert affected BA services at Terminal 5 and “impacted operation of the airfield for a short while”.

"Heathrow experienced a fire alarm activation that impacted the operation of the airfield for a short while," said the airport in a tweet.

A Heathrow spokesperson added: “As a result of the temporary closure of Heathrow Airport's air traffic control tower earlier this afternoon [Wednesday], a small number of flights from all airlines were forced to divert to alternative airports.”