Thank you so much Baxter. I hadn't noticed the Garter motto on the badge. As the motto does not seem appropriate for any organisation I wonder if some how the badge is associated with the Order of the Garter?
Thank you also for the photo of the Duchess's sapphire and ruby choker. It reminded me of the choker Queen Mary wore, but of course they are two different jewels. [This portrait is from the National Portrait Gallery, UK]