The workers will now take industrial action on 4, 5, 6, 9 and 10 May and then again on 25, 26, 27 May.

The action, planned by union Unite, will inevitably cause disruption and delays at the airport, including over the weekend of the King’s coronation.

The 1,400 security officers also took 10 days of strike action over Easter, which caused considerable disruption at the airport and resulted in hundreds of flights being cancelled.

Sharon Graham, Unite general secretary, said: “Yet again, we have a chief executive in John Holland-Kaye who thinks it is acceptable to boost his earnings by an eye watering 88%, from £800,000 to a staggering £1.5m, while he denies his own workers a decent pay rise.

“This dispute is bound to escalate with more workers being balloted and disruption set to continue throughout the summer.”

Earlier this month, Unite warned that the endemic low pay was likely to create an exodus of security staff from the airport. A survey of security officers undertaken by Unite revealed that more than one in three (35%) were planning to leave their roles.

Real-term pay cut since 2017

Wayne King, Unite regional co-ordinating officer, said: “Strikes next month will cause further disruption to airport passengers but this dispute is a direct result of Heathrow’s stubborn refusal to make an offer that meets our members’ expectations.

“Our members have been crystal clear they are seeking a substantial permanent increase in pay. A small one-off lump sum payment will not alleviate the financial pressures our members are facing on a daily basis.

“While the CEO can enjoy a lavish millionaire’s lifestyle, our members struggle to pay the bills and put food on the table. This is about need not greed.”

According to Unite, the current average salary of a Heathrow security officer is £30,000. This is made up of a basic £26,000, after three years’ experience, with a £4,000 shift allowance. It says this equates to a 24% cut in real terms since 2017.