The socialite, 37 - who is an ambassador for the organisation - and Ceawlin Thynn, 8th Marquess of Bath, 49, both appeared in high spirits as they chatted with the royal during tonight s glitzy event.
The Marchioness of Bath, 37, showed off her natural good looks in the strapless floorlength gown with an asymmetric neckline and tulle A-line skirt for the London show.