Around 5,000 protesters marched on the British parliament Saturday demanding greater action on climate change, exactly two months ahead of the general election.
Designer Vivienne Westwood, who was giving a show at the Paris Fashion Week but sent a video message, said: "I believe this demo is super important for the whole world.
"We must keep up the fight against climate change -- the clock is ticking."
Caroline Lucas, the Green Party's only lawmaker, told the crowd: "What's lacking isn't the technology, isn't the money -- what's lacking is simply the political will."
The London march was led by a man with green leaves attached to his head, who was riding a bicycle with large wings bearing the slogan: "Look after your mum."
Some demonstrators sat and meditated before the rally, while others held soil as they sang and chanted. Masked anti-capitalist protesters, dressed in black, also attended.
The general election will being held on May 7, with opinion polls predicting a hung parliament in which either Prime Minister David Cameron's Conservatives or the Labour opposition could have the most seats.
John Sauven, executive director at Greenpeace UK, said: "We can have clean energy, we can have clean jobs, we can have clean power if everyone on this planet is to stick together.
"This year is going to be the most important year, this is going to be the start of the biggest mobilisation we have seen on this issue of climate change."