Officers were forced to close roads around the centre when a number of demonstrators caused “significant disruption” to the local area, forcing shops to shut their doors for their staff’s safety.
Pictures and videos on social media showed some protesters clashing with officers as they tried to enter the building on Saturday afternoon.
The Metropolitan Police said that three separate protests took place in London on Saturday, two of which concluded “without incident”.
In a statement shared on Twitter at around 6.30pm, the force said: “The 3rd demo is now at Westfield and is causing significant disruption to the local community and businesses, police are at the location.”
At 7.45pm, it added that the incident had finished and officers had withdrawn from the scene.
The Met Police also said late on Saturday that four arrests had been made in relation to protests in London, although it was not initially clear at which protests the arrests had taken place.
“As of 21.45hrs on Saturday, 29 May, four arrests have been made during a number of protests in London,” a spokesperson for the force said.
“Four men were arrested on suspicion of offences including assault on police, violent disorder and criminal damage.”
Earlier in the day, a large crowd of people gathered in Parliament Square to protest the government’s response to the Covid-19 crisis, with some demonstrators claiming that the pandemic was a hoax.
One man, who did not give his name, told the PA news agency that he had come “because I want to be free and I want you to be free and the government are lying to us”.
Another protester said she had attended the event because the press “are lying to us” about the pandemic.
By around 1.20pm, the crowd started to disperse and head towards Hyde Park before a group of demonstrators ended up at the shopping centre in west London.
Additional reporting by PA