Last week, guards at the UK's largest airport announced an escalation of strike action, with walkouts to take place nearly every weekend from mid-June to the end of August.

Two thousand staff were due to strike on Saturday 24 and Sunday 25 June but the walkouts have been called off as a "gesture of goodwill", the union said, as staff are balloted on an "improved" pay offer.

But the Unite members could still walk out for 29 days across the summer, if the latest proposal is rejected by the union.

The offer is understood to include a 10% pay increase backdated to 1 January, effective from workers' July payslip; a further pay rise of 11.5% from October and a guaranteed inflation-linked pay increase for 2024.

Staff working in terminals 3 and 5, plus campus security who check all workers and worker vehicles, are voting on the offer from Tuesday 13 to Friday 23 June.

A Heathrow spokesperson said: "We are pleased to have agreed a pay deal which unions are recommending their members to accept.

"This a great deal for colleagues, giving them two years of guaranteed above-inflation pay rises, alongside further benefits and assurances that they told us they wanted.

"We encourage them to accept the deal so that everyone can have certainty and the backdated pay increase that so many have been waiting for."

If the offer is rejected 29 days of strikes will take place on:

• June
28, 29 and 30

• July
14-16, 21-24, and 28-31

• August
4-7, 11-14, 18-20 and 24-27

No flight cancellations are expected if the strikes do go ahead as the airport said previous strikes "failed to disrupt".