Environmental protesters have threatened to bring London to a standstill as they attempt to disrupt some of the capital's busiest areas and force the Government to declare a climate emergency.
Activists have pledged to block five central locations including Parliament Square in a non-violent act of resistance and rebellion that campaigners say could go on for weeks.
Thousands of people will converge on Marble Arch, Oxford Circus, Waterloo Bridge, Piccadilly Circus, as well as near Parliament, peacefully blocking traffic and creating a "festival" of action including people's assemblies, performances, talks, workshops and food, campaign group Extinction Rebellion said.
The movement, which is demanding the government takes urgent action on climate change and wildlife declines, has received support from actress and activist Dame Emma Thompson and former archbishop of Canterbury Dr Rowan Williams.
Speaking at a meditation on the eve of the protests Dr Williams said humans had declared war on nature.
He said: "We are here tonight to declare that we do not wish to be at war. We wish to make peace with ourselves by making peace with our neighbour Earth and with our God."
Thompson has previously said of the demonstrations: "It is time to stand up and save our home."
Organisers said: "The International Rebellion begins and Extinction Rebellion will be bringing London to a standstill for up to two weeks.
"They will be blocking five of the city's busiest and most iconic locations in a non-violent, peaceful act of rebellion where they invite people to join them for several days of creative, artist-led resistance."
Demonstrators arrived at London's Hyde Park on Sunday, some having journeyed to the city on foot in recent weeks from various parts of the UK for what is described as an "International Rebellion".
Monday will see people in at least 80 cities in more than 33 countries hold similar demonstrations on the same environmental issues, campaigners said.
While organisers encouraged people to set up camp in Hyde Park overnight into Monday, they have been warned they could be breaking the law by doing so is an offence under Royal Parks legislation.
A spokeswoman for The Royal Parks said Extinction Rebellion had not asked for permission to begin the protest in the park and that camping is not allowed.
Police said their operational response to camping "would be dependent on what if any other issues might be ongoing at the time".
Scotland Yard said they have "appropriate policing plans" in place for the demonstrations and that officers will be used from across the force "to support the public order operation during the coming weeks".
Police advised people travelling around London in the coming days to allow extra time for their journey in the event of road closures and general disruption.
Aine Fox is a reporter for the Press Association. Image (c) Press Association.