Labour leader Jeremy Corbyn told the crowds gathered in central London for a march against climate change that they had a message for the politicians gathering in Paris for talks next week - "Do what you are sent there to do."
Thousands of people set out on a march through the capital from Hyde Park to Whitehall in an effort to persuade world leaders to reach agreements on global warming.
They were part of a worldwide movement, with almost 2,500 similar events taking place across the planet.
Addressing the crowds alongside a host of other speakers, Mr Corbyn said: "The issues facing the world in Paris this week are pollution, climate change, inequality, environmental refugees, war refugees and resources wars.
"If we are to make a real difference in Paris, all these issues have got to be thought about and addressed."