Boris Johnson has warned the public that fresh air does not provide immunity against coronavirus and they should stay two metres apart.
The prime minister has told Britons that open spaces like parks are important for people’s well-being but they should follow social distancing rules and take government advice seriously.
He said: “It’s crucial that people understand that tomorrow that the schools are closed.
“I want, of course I do, people to be able to go to the parks, open spaces and enjoy themselves.
“It is crucial for health, physical and mental well-being.
“But please follow that advice and don’t think that fresh air in itself automatically provides some immunity.
“Take this advice seriously, follow it, because it’s absolutely crucial.”
There have been warnings that some major parks in London could be shut if social distancing advice is not followed amid large numbers of visitors.
The Royal Parks, which maintains those parks and five of London’s other largest open spaces, posted on Twitter: “After scenes of crowds not #SocialDistancing yesterday we want to urge you again to follow the government’s advice and keep a safe distance from others.
“We have a shared responsibility to keep London’s parks safe for everyone who needs them.
“We will keep this situation under constant review. If people do not follow social distancing guidelines, we will have no choice but to close the parks.”
Hammersmith and Fulham Council have already shut their parks from 7pm on Sunday “until further notice”, while Kew Gardens has been shut “as a precaution to limit the spread of coronavirus”.
Victoria Park and Columbia Road flower market in east London were also pictured as being full of people on Sunday.