Guests included Emilia Wickstead, Richard James, Rupert Sanderson and Stephen Jones.
The retailer recently hosted launch parties to mark the collaboration in Los Angeles, San Francisco, Paris and New York.
She wore a soft blue coat from Emilia Wickstead with Kiki McDonough earrings.
“If I were covered in fur than it might be a little bit easier,” said Rose Leslie.
Cameron has moved quickly on her clothing venture after leaving Downing Street.
The night before the British Fashion Awards, designers came together at the Moda Operandi HQ for Champagne and cocktails.
The prize for emerging design talent is in its seventh year.