Scuffles broke out as police moved in on demonstrators in Trafalgar Square, who fashioned human blockades in an try to forestall arrests and compelled officers to maneuver again.
Elsewhere, demonstrators superior on police whereas shouting “choose your side”.
Officers in riot gear and police horses might be seen on standby because the largely peaceable demonstration continued.
The Resist And Act For Freedom rally is the newest in a sequence of protests by a wide-ranging coalition of teams who oppose lockdown restrictions.
Several people held up signs opposing vaccinations and 5G technology, while others waved St George’s flags.
The crowd cheered as a speaker told them that coronavirus was a “novel coronavirus, like a novel, like a story – it’s all made up”. Another woman claimed that 5G “grows cancer”.
One protester held a banner calling for the government’s Sage scientific advisers to be sacked, while another’s declared Covid-19 a “hoax”.
The protest had been advertised by organisers as an “medic-focussed event with expert speakers, NHS and police whistleblowers. Protecting our families, our elderly and our children”.
The speakers included high-profile conspiracy theorists who have been speaking at a number of similar rallies in recent months.
A lead organiser is a nurse whose registration was suspended by the Nursing and Midwifery Council in July for spreading false information about coronavirus and vaccines.
Other speakers included the chair of the right-wing Irish Freedom Party, a Republican politician from Minnesota and prolific anti-5G campaigner Mark Steele, who was jailed for shooting a teenage girl in the head in the 1990s.
It comes amid concern that the spread of disinformation on coronavirus and potential vaccines will worsen the pandemic.
A further 16 people who tested positive for coronavirus have died in hospital in England, bringing the total number of confirmed reported deaths in hospitals to 29,735, NHS England said on Saturday.
Professor Neil Ferguson, whose modelling led the government to order the lockdown in March, urged ministers to act “sooner rather than later” as cases rise.
Boris Johnson is to consider new restrictions across England after the latest figures showed new infections doubling every week, with the R rate between 1.1 and 1.4.
“We are now seeing a second wave coming in. We are seeing it in France, in Spain, across Europe – it has been absolutely, I’m afraid, inevitable we were going to see it in this country,“ he said on Friday.
The “rule of six” came into force on Monday to restrict private social gatherings, but protests are exempt if they are organised in accordance with guidelines.
Ministers are thought to be looking at a temporary two-week ”circuit break“ in an attempt to break the chain of transmission.
The move could see pubs and restaurants ordered to close or face a 10pm curfew, while socialising between households could be banned.
Tougher new restrictions have already been imposed in large parts of England’s north west, West Yorkshire and the Midlands.