Leonardo DiCaprio; (inset) Nakul Kamte

At first, I was told 'Don't look at Leo, don't talk to him, but once they realised I was okay, we spoke," sound engineer Nakul Kamte recalls as a faint smile plays on his lips. He's the man behind the on-location sound and audio mixing for Before the Flood, a documentary on climate change that's directed by Fisher Stevens, and produced and hosted by Hollywood star, Leonardo Di Caprio.