And according to onlookers on the day, the pair were in very high spirits as they mixed and mingled with guests.
So much so, that one image of Prince William and wife Kate Middleton captured on the day appears to show the duo dancing in the streets.
The photo, taken by attendee Lucy Stafford, shows the Duchess looking like she is about to twirl around while sporting a big smile and gazing lovingly at her husband who is holding her arm.
However, Lucy recently revealed just what the royal couple were up to when she snapped the playful shot.
"As they were leaving the party, Kate was spending a lot of time talking to guests and William had to hurry her along, which is the moment the photo was taken," Lucy told Hello!
"I feel so fortunate to have attended the party and will never forget it."