The dispute is over pay, and there have already been similar strikes in recent weeks by campus security and staff in terminal five, which were not disruptive.

Passengers are advised to check with their airline for the latest information on baggage allowances during the periods of industrial action, which will coincide with the beginning of the school holidays and the August bank holiday.

Heathrow said it will do everything it can to minimize strike disruption, but Unite has said the dispute could escalate further in the coming weeks and that Heathrow security officers are paid less than others at major airports in London and the South East.