Thousands of people have descended on central London to protest against mass coronavirus vaccinations.
Some branded the Covid-19 pandemic a "scam", while others read: "Save our rights. No mandated vaccines."
One protester held a banner calling for the Government’s Sage scientific advisers to be sacked, as another’s declared Covid-19 a “hoax”.
Organisers sold t-shirts bearing 5G conspiracy theories and advocating the legalisation of cannabis as a range of speeches were made to the crowd.
Addressing the crowd to huge cheers, organiser Kate Shemirani said: “We are the resistance.”
Scuffles broke out between some demonstrators and police, with officers moving in on protesters as they congregated near Nelson's column.
The protesters formed human blockades opposite the officers to stop them from making arrests.
Disputes broke out between the two sides next to the National Gallery, before officers were pushed back by the loud crowd, who began cheering and chanting.
Riot police go in at Trafalgar Square protest - police telling everyone to move back pic.twitter.com/ycbbhlQzkt— Fran Le Noury (@franlenoury)September 19, 2020
Dozens of Metropolitan Police officers, including some on horseback, later moved in for a second attempt to break up the gathering in Trafalgar Square.
Traffic was brought to a halt as protesters erected a blockade in a bid to prevent officers from making arrests.
One protester hit a London taxi after the driver beeped in frustration. The protester then appeared to spit through the window at the driver.
A University College Dublin professor told the anti-vax rally the coronavirus vaccine will “make people sick”.
Professor Dolores Cahill told the crowd: “We want freedom, truth and love.
“I know that vaccines make people sick, you should not trust the Government, the doctors and the media, they are lying about the Covid-19 vaccine.
“Vaccines have not been safety-tested, they tell you when you take a vaccine you’ll get a little bit of swelling, is that true? No.
“You can get multiple sclerosis and allergies, when I talk to parents, there are 12 known diseases you can get.
“If you’re a parent, auntie, grandparent, cousin or neighbour, we’re here to say the truth will come out.”
Early on in Covid-19 outbreak in Europe, World Health Organisation (WHO) director-general Dr Tedros Adhanom Ghebreyesus had issued a warning about the dangers of misinformation around the virus.
"I would also like to speak briefly about the importance of facts, not fear," Dr Tedros said. "People must have access to accurate information to protect themselves and others."
He added: "At the WHO we're not just battling the virus, we're also battling the trolls and conspiracy theories that undermine our response."
Prime Minister Boris Johnson has previously described anti-vaxxers as "nuts".
Speaking to nurses at a London GP surgery in July, the Prime Minister said: "There's all these anti-vaxxers now. They are nuts, they are nuts."