The Princess opted for a selection of emerald jewels to tie in with her green dress, and her choker was particularly spectacular.

Queen Mary’s Art Deco Emerald Choker features several statement green gems surrounded by diamonds, and it is a royal heirloom.

The piece was commissioned by Queen Mary, the late Queen Elizabeth’s paternal grandmother, from the royal jeweller Garrard in the 1920s.

The Queen was thought to have given Princess Diana the jewel as a loan when she married Prince Charles in 1981, and it became a firm favourite for formal engagements.