A passenger arriving at Heathrow said he wasn't told about the UK's new 14-day quarantine rules which came into force today.
The man, who arrived from Switzerland, said he didn't know he had to self-isolate for two weeks to help guard against a second wave of coronavirus.
The passenger said he was feeling unwell but had symptoms not related to Covid-19. He planned to take the Tube into central London.
All passengers – bar a handful of exemptions – should fill out an online locator form giving their contact and travel details, as well as the address of where they will isolate.
People who fail to comply could be fined £1,000 in England, and police will be allowed to use “reasonable force” to make sure they follow the rules.
The plans have been met with strong criticism from opposition parties and some Conservative MPs – as well as the travel industry.
British Airways has begun legal proceedings over what it calls the government’s “unlawful” quarantine measures.