Johnson issued a plea for those who are able to work from home to do so until the virus is under control -- just weeks after the government launched a high-profile campaign encouraging people to return to their offices and workplaces.
And he announced that face masks will be made mandatory for staff in the hospitality and retail sectors, and for passengers in taxis. Masks are already required on public transport, and for customers in shops. Moreover, the masks mandate will become law, not just guidance.
Addressing the nation from 10 Downing Street in a pre-recorded message, the Prime Minister said: "Never in our history has our collective destiny and our collective health depended so completely on our individual behaviour. If we follow these simple rules together, we will get through this winter together. There are unquestionably difficult months to come. And the fight against covid is by no means over."
He described his reluctance "to make any of these impositions, or infringe anyone's freedom," but added that "unless we take action, the risk is that we will have to go for tougher measures later."
Citizens and businesses who violate the rules will face fines; the government is to provide extra police funding to help them enforce the restrictions. The police will even have the option to request military support, should they become overwhelmed. That doesn't mean troops patrolling the streets: Downing Street said the military could be used to fill office roles and to guard protected sites, freeing up the police to enforce the virus response.
Johnson said the measures could remain in place for six months if the situation didn't improve, meaning large gatherings over Christmas could be impossible for many families.
The new rules apply only to England. Health policy in the UK's other three nations, Scotland, Wales and Northern Ireland is determined by their devolved administrations; they are also expected to tighten restrictions in the coming days.
The announcement comes at a critical time for the UK, a country whose first wave of Covid-19 led to the most deaths of any European country and the worst recession of any major economy.
But exactly what should be done to tackle the UK's huge coronavirus problem is a matter of fierce political debate.
Johnson's new measures will displease members of his own governing Conservative party on both sides of the debate, including those in his own Cabinet.
The pandemic has revealed a split between those who think the government should prioritize the UK's economic recovery, after GDP dropped by 20.4% in the second quarter of 2020, and those who believe that avoiding a second wave of Covid-19 has to be the priority.
Senior figures on the right of the party fear the long-term impact of economic damage and job losses will be more costly than the virus itself; those on the other side of the debate say the economic hit of a second, short, "circuit breaker" lockdown is worth it to save lives.
The relatively modest measures unveiled by Johnson on Tuesday appear to be an attempt to appease both sides; the PM told parliament he would "not listen those who say let the virus rip," nor to those who want a state of "permanent lockdown."
Critics have already noted that Johnson's government only recently urged the nation to get back to the office, in order to save high street businesses like sandwich shops and pubs that have suffered from the lack of day-to-day trade from commuters.
The government also introduced a popular "Eat Out to Help Out" scheme, which saw diners offered discounts of up to 50% per head to eat at restaurants whose doors had earlier been forced to close by the pandemic.
Johnson has been facing the toughest few months of his difficult premiership.
Not long ago, public health experts were talking about the real prospect of a second wave meaning the government would have to choose between pubs and schools.
At the time, government officials said that this framing was crude and that the pandemic could not be viewed as a zero-sum game. They believed it was possible to have their cake and eat it.
But with cases rising and the country preparing for what could be a brutal winter, Johnson may soon have to make choices that will be framed as the economy versus public health, or personal freedoms versus national lockdown.
And that is not a position any small-state, liberal Conservative Prime Minister ever dreamed they'd be in.
CORRECTION: An earlier version of this story misstated how long the new restrictions will be in place for. The story has been updated to reflect that they could be in place for six months, depending on circumstances.