Thousands of anti-lockdown protesters marched through central London on Saturday, with Parliament and Prime Minister Boris Johnson's Downing Street residence pelted with tennis balls.
England was meant to have lifted all restrictions on June 21 but a rise in coronavirus cases owing to the emergence of the Delta variant, first identified in India, delayed those plans by at least four weeks.
Protesters marched from Hyde Park, along Oxford Street and towards Parliament carrying flags, whistling and shouting as they demanded an immediate end to restrictions.
There were widespread calls for health minister Matt Hancock to resign after he admitted breaking Covid-19 guidance by kissing and embracing an aide in his office.
The Metropolitan Police said they made 12 arrests.
"The main reason I'm here is because I feel this lockdown has come at the cost of our liberty and rights," said Iain McCausland, who travelled from Devon on England's south-west coast to take part.
"Our freedom to assemble, our freedom to travel and work. I'm really quite angry with the government, so is everyone here."
One placard demanded "arrest Hancock", in reference to the former health secretary, who hit the headlines on Friday after CCTV footage emerged of him kissing an aide inside a government office.
On Saturday he announced his resignation and Sajid Javid will take up the role.
Mr Hancock, 42, had been at the centre of the government's fight against the pandemic, routinely telling people to follow strict rules and even welcoming the resignation last year of a senior scientist who broke restrictions in a similar manner.
Last year, Mr Johnson's then most senior adviser Dominic Cummings broke the rules at the height of the pandemic.
It led to accusations that members of Mr Johnson's government believed themselves to be above the law.