William and Kate were reportedly devastated after Prince Philip's death

Prince William and Kate Middleton had a hard time coming to terms with Prince Philip's tragic demise.

A 'Thank You' card mailed to constituents who sent their condolences on behalf of the Duke and Duchess read, “They will all miss their much-loved grandfather and great-grandfather, but your message has provided great comfort at this difficult time,” the message, shared by the blog Gert’s Royal Replies, said.

The card, which Gert’s Royal Replies noted had a shimmer finish and thicker card stock than other royal photocards, also said, “The Duke and Duchess of Cambridge thank you for your kind words following the death of The Duke of Edinburgh. Their Royal Highnesses have been incredibly moved by the many thoughtful messages they have received in recent weeks.”

Gert’s Royal Replies said the card would “probably be a much more treasured memento from recipients than their usual photo card,” so it was “nice that they made this something that would last an extra long time.”

The Royal blogger said the card’s black border signifies “mourning” as per an “old Victorian-era tradition.

“While some royals use this black mourning edging, it’s not required that all royals use it,” they also noted on their website.