Rabbis, priests, Muslim campaigners and government policy advisers gathered for the inaugural conference of Faith for the Climate at St John's Waterloo last week.
Their mission: to tackle the urgent question – how should religions respond to climate change?
Among the speakers was Sir David King, special representative to the foreign secretary on climate change, and Dr Husna Ahmad, CEO of Global One and author of The Green Guide to the Hajj.
"Only when we think as one humanity can we save the planet," said Dr Husna Ahmad, to loud rounds of applause, while Bishop Nicholas Holtam, the Church of England's lead bishop on climate change warned: "There is no Planet B. This is our common home."
Canon Giles Goddard, vicar of St John's Waterloo and co-chair of the event, said afterwards: "Opportunities for urgent interfaith action do not come around very often. But climate change focuses the mind and produces genuine exchange. If your mosque can reduce its carbon footprint, how did you do it, and can the rest of us do the same?"
Climate change is climbing up the agenda for faith groups. Last year, the Church of England's General Synod voted to stop investing in two of the most polluting fossil fuels – tar sands and thermal coal.