Prince Andrew hosted the daughter of Victoria and David Beckham for a tea party at his palace apartment last week.
They look directly onto Buckingham Palace.
The show is one of three exhibitions highlighting Queen Elizabeth’s dress over 90 years.
The British monarch made a rare public outing on Monday night for a dinner at Bellamy restaurant in central London.
Massenet is chairman of the British Fashion Council, and the founder and former executive chairman of Net-a-porter Group.
Mary McCartney took the photo to mark a royal milestone.