This time, however, he fears that the images of shattered windows and burned police vehicles will help Prime Minister Boris Johnson pass the police law, which has already cleared two key hurdles in Parliament.

“The consequences of what they’ve done is to increase the likelihood of that bill winning support,” Mr. Rees said.

For many in Britain, that would be a bitter irony, given that the pandemic has already led to the greatest restriction of civil liberties in recent memory. Coronavirus regulations that were expected to last no more than a few months have now been in place for a year, causing tensions between police and the public not just at protests, but also at house parties and even with those meeting outside for coffee.

Early in the pandemic, one local police force used drones to shame a couple walking a dog on a lonely path. The owners of gyms and sports clubs were raided by police when they opened against the regulations.

An earlier version of the government’s coronavirus regulations contained a provision that allowed nonviolent protests. But that was removed from a later version, leaving the right to peaceful assembly in a kind of legal limbo. Under the latest draft of the rules, issued on Monday, protests would be allowed under limited circumstances, starting next Monday.

These emergency laws were rushed through Parliament without the scrutiny normally applied to legislation. Lacking a written constitution, Britons who want to take to the streets have to rely on the less clear-cut protection of a human rights act.

By contrast, Germany’s Federal Constitutional Court last year upheld the right of its citizens to protest, provided that they adhered to social distancing rules.

“This pandemic has exposed the weaknesses of our unwritten constitution when it comes to certain rights,” said Adam Wagner, a human rights lawyer and expert on the coronavirus rules. “If you take representative democracy from the process of lawmaking, you miss out on key voices.”

The government makes other arguments for the policing bill. Cabinet ministers note, for example, that the security costs of protecting a new high-speed rail link from environmental protesters has been 50 million pounds, or $69 million.

Priti Patel, the home secretary, condemned the clashes in Bristol has “thuggery and disorder” and said protecting the police was the government’s top priority — though not, she added, of some members of the opposition.

“We have been clear that to save lives and fight this pandemic, people must not currently hold large gatherings,” she said in a statement to Parliament. “Too many this weekend selfishly decided that this did not apply to them.”

Further raising the political temperature, the policing bill is moving through Parliament at the same moment as the government’s renewal of its coronavirus regulations, which also drew fire from the libertarian right.

“The Coronavirus Act contains some of the most draconian detention powers in modern British legal history,” said Mark Harper, who chairs the Covid Recovery Group, a caucus of Conservative lawmakers critical of the lockdown rules.

While many say the debate on the role of the police in Britain is overdue, some sympathize with the plight of the officers. They are caught between politicians and the public, with a nebulous constitutional status and a shifting set of rules to enforce, particularly during a public health emergency.

“It’s not the fault of the police that the coronavirus regulations are in part necessarily draconian and in parts unnecessarily draconian,” said Shami Chakrabarti, an expert in civil liberties and a Labour Party politician.

The bigger problem, she said, is that Britain tends to conduct debates about the role of the police after wrenching episodes like a police shooting, the killing of Ms. Everard or the violent clashes in Bristol. This inflames public opinion in one direction or the other, she says, but can get in the way of a thoughtful debate.

“We almost only ever have this discussion in moments of crisis,” Ms. Chakrabarti said, “not in peacetime.”

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