Despite the capital and parts of the south-east having moved to Level 3 to tackle the increase in coronavirus cases, protesters are expected to attend the rally in Parliament Square on Saturday, December 19.
Met Police wrote an open letter urging people not to attend large gatherings the past weekend before Christmas.
Assistant Deputy Commissioner Laurence Taylor said: “When we become aware of planned events that will violate the rules, we will try to engage with the organizers or the venues to make them fully aware of the restrictions that are in place to keep people safe. .
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“However, if people don’t listen to our advice and play by the rules, we will be forced to take enforcement action.
“With infection rates rising rapidly across the capital, we must all play our part in preventing the spread of the virus.
“It’s the last weekend before Christmas, so now is not the time for complacency. I know Londoners know what they should and shouldn’t be doing and I urge everyone to act reasonably and do their part to keep our city safe.
“It is more important than ever to follow the guidelines put in place to keep us all safe and healthy.
“This weekend we will make sure we manage the activity of a few so that we do not put our communities at even greater risk during this pandemic.
Some 11 people were arrested on Monday after a protest by around 200 protesters in Parliament Square in London for suspected offenses, including violation of Covid-19 regulations, breaches of public order law and lanes de facto on an emergency worker.
In the second nationwide lockdown at the end of November, more than 150 people were arrested as activists marched from Hyde Park to Oxford Circus and Regent Street, clashing with police.
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