Activists from Beyond Politics roadblocked Trafalgar Square on Saturday (July 25) demanding the UK government steps down and is replaced with citizens' assemblies.
Police attempted to negotiate with protesters who refused to move from the road.
Roger Hallam, a co-founder of Extinction Rebellion, spoke at the event and compared the current situation to the French Revolution.
Hallam made headlines last year after he called the Holocaust "just another f***ery in human history", which lead to German publisher Ullstein pulling his then-upcoming book.
Beyond Politics caused controversy earlier this week after they threw pink paint at NGOs including Greenpeace and Amnesty International, accusing them of not doing enough.