Priti Patel's officials were repeatedly warned last year about the growing crisis over queues at Heathrow forcing passengers to wait for hours. The airport wrote twice to the Home Office – in August and December – to say urgent action was needed, including more Border Force staff to tackle lengthening queues that meant planes had to be delayed and passengers held on board jets. The disclosure follows a warning on Wednesday by Chris Garton, Heathrow's chief solutions officer, that the situation had become "untenable" as passengers faced queues of up to six hours despite arrivals being more than 80 per cent below normal. There is growing alarm that the new rules requiring 100 per cent checks on all passengers' locator forms will lead to chaos when international travel begins to resume in earnest from May 17 unless the process is computerised and extra resources deployed. "Maximum queue times are exceeding three hours almost every day, and at times reach six and a half hours despite 86 per cent fewer passengers. It is inhumane for Border Force to keep people waiting so long," said a Heathrow source. "The Home Office must simplify and automate processes and adequately resource Border Force in the meantime." Last August, Heathrow wrote to the Home Office warning that queues were already up to two hours and there was an "urgent need" to ensure passengers filled out their forms correctly before they arrived at immigration control desks. Border Force officials warned this week that just one passenger without a properly completed form could delay a queue by 30 to 40 minutes. In December, Heathrow repeated its warning from last summer, saying queues had hit three hours, forcing it to "slow inbound traffic and hold passengers on board". The row came as the boss of TUI, Europe's largest tour company, said successful vaccine programmes would prevent another washout for summer holidaymakers. "We are optimistic about the summer," said Friedrich Joussen, whose company owns a fleet of aircraft, cruise ships and a chain of travel agencies. Mr Joussen said bookings in March alone had hit 2.8 million, and as a result the company expected to operate up to 75 per cent of its normal schedule for the summer season. "We are still confident that we will have a decent summer," he added, pointing to coronavirus vaccination programmes in the UK, US and Europe. The company, which sells holidays to 180 different countries, suffered heavy losses during the pandemic.