The parents-of-two, who were seen yesterday at the Chelsea Flower Show, included the candid photograph with a thank you card sent out to their biggest royal fans.
Protocol normally dictates that the official Kensington Royal account will share new images of the family, but this was exclusively for members of the public who Kate and William wanted to thank.
Paul Ratcliffe, royal photographer, sent the pair a card on their fifth wedding anniversary back on 29 April and received the unexpected thank you note in the post this week.
The card read; ‘The Duke and Duchess of Cambridge were so touched that you took the trouble to write as you did on their fifth wedding anniversary. It really was most thoughtful of you and Their Royal Highnesses send you their warmest thanks and best wishes.’
Lovely thank you card received from TRH The Duke & Duchess of Cambridge for their 5th Wedding anniversary pic.twitter.com/YXKpytnZvC— Paul Ratcliffe (@pdratcliffe) May 25, 2016
The photographer decided to share the memento on his social media pages, with his 300 followers, not realising the impact it would have.
Clearly pleased with the card, Paul captioned the initial image; ‘Lovely thank you card received from TRH [Their Royal Highness] The Duke and Duchess of Cambridge for their 5th wedding anniversary.’
Then, a couple of hours later, added; ‘Who would have thought my Twitter would go into meltdown after I received a thank you card from the Cambridges!’
Lots of people have now commented speculating about the origin of the photograph, with many believing it was taken by Chris Jelf who took the family’s Christmas pictures.
Who would have thought my twitter would go into melt-down after I received a thank you card from the Cambridges!! pic.twitter.com/mNx8fiAtsA— Paul Ratcliffe (@pdratcliffe) May 25, 2016
Earlier today the couple were overheard lovingly referring to each other with nicknames.
At the Buckingham Palace Garden Party, Kate called her husband ‘babe’ whilst William referred to his wife as ‘darling’ on more than one occasion according to bystanders.