Heathrow has reopened Terminal 4 as a dedicated facility for processing arrivals from red list countries.
It said the measure would keep those arriving from destinations on the high-risk list away from other travellers.
The red list has been resurrected with 10 countries in southern Africa put on it on 26 November due to concerns about the Omicron coronavirus variant.
People entering the UK from those locations must spend 11 nights in a quarantine hotel. The cost is estimated at £2,285 for solo travellers, reports BBC.
Heathrow first opened a facility for red list arrivals at Terminal 3 in June following concerns that allowing passengers to mix with those who had flown in from other locations could increase the spread of the virus.
It was later switched to Terminal 4 but this was closed in early November following the removal of the final seven countries on the list.
The facility was reopened at 15:00 GMT.
Tougher travel rules introduced by the government include requiring fully vaccinated people entering the UK to self-isolate until they receive a negative result from a PCR test.
Previously they were only required to take a cheaper lateral flow test and did not need to self-isolate unless their test result was positive.
Heathrow’s chief operating officer Emma Gilthorpe said the rapid introduction of restrictions for international travel would be a “significant blow for British exporters and those wanting to visit friends and relatives”.
She added: “Keeping the changes under constant review, and a government commitment to the removal of red list countries as soon as it is safe to do so, will help.
“Heathrow maintains the highest levels of Covid-secure measures to ensure our passengers, colleagues and partners know that Heathrow is a safe place to travel to and from.”
