The event asked those attending to "consider the environment" when picking their outfit.
Chatelaine
The Queen has begun using the accoutrement during public appearances, proving once again that she's wise beyond her years.
She paired the elegant outerwear with a matching green top, black heels and dark trousers.
The suit was from Emilia Wickstead, one of Kate's favourite designers.
The cape-effect sequinned gown was by Jenny Packham.
