On 11 December 1997, delegates from 160 countries worked through the night in Kyoto, Japan, to agree the first international treaty to cut greenhouse gas emissions. Some countries present did not ratify it, notably the United States. But it was the first agreement of its kind. We talk to two people who helped make it possible - a young UN intern, Joanna Depledge, and her boss, the chair of the negotiations, Raul Estrada-Oyuela.

(Photo: Delegates at the opening session of the Kyoto Protocol negotiations. Credit: Toru Yamanaka/AFP/Getty Images)