Dame Vivienne Westwood and Naomi Campbell will forever be linked by a moment in catwalk history: when the supermodel toppled off her vertiginous heels on Westwood's runway in Paris in 1993 (and reacted by throwing her head back in peals of laughter). But they have other things in common, too. Namely a shared passion for activism and philanthropy. Watch the video to see the long-time friends discuss social injustice and the threat of climate change – as well as what really caused fashion's most famous fall...