Environmental campaign group Extinction Rebellion has kicked off their fifth mass protest in Trafalgar Square, as they begin two full weeks of climate rallies.
Hundreds descended on the capital on Monday in a bid to demand the government divest from fossil fuel companies.
Demonstrators were spotted marching from St James’ Park banging drums and blowing whistles, while a marching band blocked Trafalgar Square.
Gail Bradbrook, co-founder of the activist group, opened the "Impossible Rebellion" with a speech sharing solidarity with nations that are disproportionately affected by climate change.
Police could be seen surrounding the protest, which is expected to disrupt London as demonstrators call attention to climate issues in the coming days.
The two weeks of activism, organised by Extinction Rebellion will take place at different locations around London.
The activist group said thousands of people are expected to take part in the protests, which plans to "target the root cause of the climate and ecological crisis".
It comes after three protesters scaled the entrance of Guildhall in central London on Sunday.
A crowd of about 200 people sang and cheered as the protesters sprayed red paint over the walls of the building and unfurled a banner reading “co-liberation freedom together”.
A wall of police officers gathered in front of the building while special officers and a JCB vehicle were brought in to remove the demonstrators at about 8pm.
The Metropolitan police said nine people had been arrested in connection with the protest.
The force said three had been arrested on suspicion of criminal damage and a further five were arrested for conspiracy to cause criminal damage.
A further person was arrested for going equipped to cause criminal damage and all are in police custody, the Met said.
Among the crowd at Guildhall was Game Of Thrones actor Jerome Flynn, who said it was “more urgent than ever” for people to take a stand together.
“I’m a bit lost for words at the moment, I’m feeling very moved to be here,” he told the PA news agency.
“It feels needed and more poignant and more urgent than ever to come together.
“It’s time to collaborate, there are so many things that are trying to polarise us and pull us apart.
“More than ever, we need to come together.
“We’ve got used to certain systems that are life destructive, we created them, we’ve become addicted to them, and we know the world is burning as a result.”