Prince William and Kate Middleton have shared details about the "difficult time" spent mourning their grandfather Prince Philip's death.
The Duke of Edinburgh was 99 and just two months from his 100th birthday when he died of "old age" at Windsor Castle on April 9.
A blog and Twitter account, Gert's Royal Replies, sends letter to the Windsors and then shares their responses online.
Gert sent the Duke and Duchess a condolence letter following Prince Philips death and received a warm note in return, which said her "kind words" were of "great comfort at this difficult time".
The reply came in a Kensington Palace envelope, emblazoned with the family's Royal Crest and with a Royal Mail stamp fixed to the front.
Prince William and Kate's own monograms, a W and a C (for Catherine) beneath a regal crown were also printed on the front of the inner card.
Inside contains a photo of the late Duke with a joyful smile while dressed in full military garb in 2012 during the Queen's Diamond Jubilee Armed Forces and Muster at Windsor Castle, Gert said.
The Cambridge's response note was typed on a card, which is bordered by a black line, which represents mourning.
The note itself reads: "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.
"They will all miss their much loved grandfather and great-grandfather, but your message has provided great comfort at this difficult time."
Following Prince Philips death in April, the Royals together released a series of never-before-publicised family photographs of him.
Many, shared on the couple's official Instagram, were of their children with their great-grandfather.
One taken at Balmoral Castle in 2015 shows William and Kate flanking the Queen and the Duke, while her Majesty gazes fondly at Princess Charlotte who's propped up in Kate's arms.
In the picture, a moment of fondness can be seen with Prince George gripping tightly to his great-grandfather's hand.
Another adorable picture shows the Duke cracking a smile as the Duchess snaps him as he mans the horses on a carriage ride with young Prince George.
The caption below, apparently written by Prince William, explains his happiness of the "special memories" his children experienced with their great-grandfather.
He was also grateful they were able to see for themselves his "infectious sense of adventure" and his "mischievous sense of humour!".
The caption reads: "My grandfather’s century of life was defined by service – to his country and Commonwealth, to his wife and Queen, and to our family.
"I feel lucky to have not just had his example to guide me, but his enduring presence well into my own adult life – both through good times and the hardest days.
"I will always be grateful that my wife had so many years to get to know my grandfather and for the kindness he showed her.
"I will never take for granted the special memories my children will always have of their great-grandpa coming to collect them in his carriage and seeing for themselves his infectious sense of adventure as well as his mischievous sense of humour!
"My grandfather was an extraordinary man and part of an extraordinary generation. Catherine and I will continue to do what he would have wanted and will support The Queen in the years ahead.
"I will miss my Grandpa, but I know he would want us to get on with the job."
Another photograph shows the Queen and her husband looking over-the-moon while surrounded by seven of their great grandchildren.
On the day of his death, the Cambridges shared a photo of the Duke wearing full military garb, and expressed their "deep sorrow" of his passing.
Before he passed, Gert's Royal Replies wrote to the Duke to wish him a speedy recovery after his hospitalisation.
The gentle note sent back expressed the Duke's thanks for consideration at the time.
"I did not expect this would be the last letter I ever wrote to him," the account reads.
