The first passengers arriving in the UK from countries at high risk of Covid infection began 10 days of isolation at airport hotels on Monday as new quarantine measures came into force to limit the spread of more dangerous variants.

Government-contracted security guards met the passengers at immigration in London’s Heathrow airport, before corralling them through baggage reclaim and on to coaches to take them to their rooms.

Each guest must pay £1,750 for the stay, during which they are confined to their room except for limited daily outdoor exercise, under escort. In England anyone returning from 33 high-risk countries must book a room through a government portal before flying back.

Arrivals by air across the UK were lower than in recent weeks following a busy weekend "as everyone who could avoid the quarantine measures did so", according to Lucy Moreton, the head of the Immigration Services Union, which represents many Border Force officers.

The Radisson Blu at Heathrow airport was among hotels to host a small number of travellers coming from high-risk countries on Monday.

Heathrow, the UK’s busiest airport, said the process had run smoothly although only a handful of visitors had returned to enter quarantine in the first few hours of the rules coming into force.

Concerns were expressed, however, that arrivals from high-risk countries were not properly segregated from other passengers in the airport and on flights. Those heading in to quarantine were, however, put into separate lanes at immigration.

Yvette Cooper, chair of the Home Affairs Select Committee, said the government risked undermining the new quarantine policy. “The whole point of these measures is to prevent new variants from spreading — but that won’t happen if there are still too many holes in the system,” she said.

Downing Street said arrivals had already been tested for the virus prior to departure, and added: “We are working closely with airlines and carriers who are ensuring that the flights they provide are Covid-secure when people arrive in the UK”.

The majority of passengers arriving from the 33 so-called “red-list” countries are expected to come in via Heathrow, where around 150 flights were scheduled to land on Monday.

Queues in the arrivals halls were less than an hour for much of the day, and the airport said it would continue to push Border Force to provide enough immigration officers in the coming days to make sure long lines do not build up.

In recent weeks, queues have stretched for as long as five hours after immigration gates were closed to ensure all passengers had completed the extra paperwork required for entry into the UK during the pandemic. Heathrow warned of the possibility of flight cancellations if more immigration officers were not deployed.

The Home Office warned passengers to expect queues on arrival “given the enhanced monitoring in place at UK airports”.

Accor, whose Novotel near Heathrow is part of the quarantine scheme, said the few guests who had been in the hotel left on Monday and the site was undergoing a deep clean in preparation for arrivals on Tuesday. Marriott, which has two hotels designated to take arrivals under the scheme, said booking numbers were “pretty low”.

Under the rules in England, only UK residents and Irish nationals can enter from the high-risk countries at five airports: London’s Heathrow, Gatwick and City airports, Birmingham and Farnborough, the latter for those using private jets. Direct flights from red-list destinations are banned, so anyone returning from there has to come via a third country.

The new rules apply to England, with the devolved governments in Wales and Northern Ireland expected to follow suit although neither currently has any international air links.

The Scottish government has applied stricter rules, requiring all international arrivals to quarantine in hotels, regardless of where they are arriving from. Aberdeen, Edinburgh and Glasgow airports will process returning residents.

The policy is part of a series of new rules that includes a requirement for arriving passengers to take two Covid-19 tests — on days two and eight after arrival — in addition to one they must take 72 hours before departure for the UK.

The travel sector has warned that the crackdown has hit the industry in what would normally be the busy half-term week as well as a crucial time for summer bookings.

“The industry simply cannot afford to wait until everyone in the UK is vaccinated before people start to travel again — otherwise insolvencies and redundancies will be inevitable,” ABTA, the trade association for the travel industry, said.

Figures released by the Office for National Statistics on Friday showed that economic output of travel agents and tour operators fell 86 per cent in December 2020 compared with February 2020, while air transport output fell 89 per cent.