I n this post-Kardashian world of celebrity influencers, where every day some fashion line or make-up range no one needs is launched, it may seem surprising to be discussing the carbon cycle with a model. But that’s exactly what I’m doing. Arizona Muse, 36, once described by Anna Wintour as “the new face of American fashion”, is drop-dead gorgeous, obviously.

She has influence, clearly. But she’s also, it turns out, a bit of a green geek. “I lost a lot of followers,” the founder of the environmental charity Dirt says about the time she swapped sexy fashion shots for posts about soil regeneration on Instagram.

“It didn’t go very well at first. But I decided that I didn’t care and I was going to carry on anyway.”.