Confusion rippled through Britain on Tuesday, a day after Prime Minister Boris Johnson ordered a three-week halt to all non-essential activity to fight the spread of the new coronavirus.

Streets were empty but some subways were full. Hairdressers were closed but construction sites were open. People in romantic relationships wondered whether they could see their boyfriends or girlfriends if they weren't living together.

The government has ordered most stores to close, banned gatherings of more than two people who don't live together and told everyone apart from essential workers to leave home only to buy food and medicines or to exercise.

“You must stay at home,” Johnson said in a somber address to the nation on Monday evening.

But even as the U.K. recorded its biggest single-day increase in COVID-19 deaths, commuters crowded onto London subway trains Tuesday, amid confusion about who was still allowed to go to work.

As of Tuesday, Britain had 8,077 confirmed cases of COVID-19, and 422 deaths, 87 more deaths than a day earlier.

Julia Harris, a London nurse, said her morning train to work was full.

“I worry for my health more on my commute than actually being in the hospital," she said.

Sporting goods chain Sports Direct said its shops would remain open, arguing that selling exercise equipment was an essential service. It reversed course after an outcry from the public and officials.

Many building sites remained open, with construction workers among those crowding onto early-morning subways.

Electrician Dan Dobson said construction workers felt “angry and unprotected,” but felt they had to keep working.

"None of them want to go to work, everyone is worried about taking it home to their families,” he said. "But they still have bills to pay, they still have rent to pay, they still have to buy food.”

Authorities sent mixed messages. British Treasury chief Rishi Sunak defended keeping construction sites open, insisting it could be done safely. Scottish First Minister Nicola Sturgeon, however, said construction sites should close unless the building work was “essential.”

Some closed voluntarily. Construction was halted on London’s huge Crossrail train project, and home builder Taylor Wimpey stopped work on all its sites.

London Mayor Sadiq Khan implored employers: "Please support your staff to work from home unless it's absolutely necessary. Ignoring these rules means more lives lost.”

Many families were also confused by the new rules.

After Johnson said people should not mingle outside of their household units, separated parents asked whether their children could still travel between their homes. Cabinet minister Michael Gove initially said children should not move between households, before clarifying that it was permitted.

As for couples who don't cohabitate, England's deputy chief medical officer, Jenny Harries, said "they should test the strength of their relationship” and decide whether to move in together.

“What we do not want is people switching in and out of households. ... Test really carefully your strength of feeling," Harries advised.

The restrictions are the most draconian ever imposed by a British government in peacetime. But they don’t go as far as lockdowns in Italy and France, where people need a document authorizing their movements.

The government said police would have powers to break up illegal gatherings and fine people who flout the rules. But some expressed doubts about whether the lockdown could be enforced.

Britain has lost thousands of police officers during a decade of public spending cuts by Conservative-led governments. Johnson has promised to recruit 20,000 more police officers, but those efforts are still in the early stages. Unlike some other European countries, Britons do not carry ID cards, another factor complicating enforcement efforts.

"There is no way really that the police can enforce this using powers. It has got to be because the public hugely support it,” Peter Fahy, former chief constable of Greater Manchester Police, told the BBC.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever or coughing. But for some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. Hospitals in Italy and Spain have been overwhelmed by the critically ill.

Intensive care departments in London, the hardest-hit city, are being inundated with COVID-19 patients. Johnson warned that the National Health Service could be overwhelmed within weeks unless people took the lockdown seriously.

The government said Tuesday that more than 11,000 retired doctors and nurses had answered a call to return temporarily to work. It also sought a quarter of a million volunteers to help deliver food and medicine to vulnerable people who have been told to quarantine themselves for 12 weeks.

And British troops have been drafted in to convert London's Excel convention center into a 500-bed hospital by next week.

Critics say British authorities have acted too slowly to avert an Italy-scale crisis. Schools were closed less than a week ago, and pubs and restaurants were only shuttered on Friday.

Andrea Collins, Senior Clinical Lecturer in Respiratory Medicine at the Liverpool School of Tropical Medicine, said the new restrictions were welcome but didn’t go far enough.

"I think we need permits across controlled areas to go to a workplace,” she said. “Home working is hard for many but it is possible, we just need to adapt to a new way of being.”