He added: "I took this ahead of the RAF 100 Commemorations at Buckingham Palace this summer - I expect you all to send your Christmas presents only using this stamp!"
And according to royal experts, there's subtle signs the Duchess is preparing for a more prominent role in the monarchy.
There are rumours the Queen will abdicate her throne in three years to allow Prince Charles to become King. Her Majesty reportedly intervened after a tense negotiation on what tiara Markle would wear on her big day.
During the event, the Queen watched from the balcony of the Foreign and Commonwealth Office building, as she did previous year.
As is tradition, Meghan will wake up on Christmas morning and drag herself along to an ~exclusive~ service at St Mary Magdalene Church in Sandringham, just like the rest of the Windsor squad.
In February, Meghan Markle was assigned her first Royal staffer, Amy Pickerill, who was previously working in Prince Harry's press office. He placed the queen's wreath at the foot of the Cenotaph monument while she watched from a balcony seat. He's already rocking shorts just like his big brother George (most royal boys wear shorts and knee socks until they are eight or so and then they start wearing trousers!) Charlotte looks adorable as ever, smiling for the camera, but also possibly eyeing something behind the camera that she wants to play with.
Melissa wasn't the only staff member to resign this year - royal director of communications Sally Osman left earlier this year, as did the queen's media secretary, Steve Kingstone, and the Duke and Duchess of Cornwall's personal secretary, Mark Leishman, Insider reports. The woman pictured aside Markle is the German President Frank-Walter Steinmeier's wife, Elke Budenbender.
Chris Jackson via Getty Images Queen Elizabeth II speaks with Prince Charles. But she has started to pass on some of her responsibilities to the younger members of her family.
These events came just one day after Prince Harry and Meghan, and Prince William and Kate, attended the Royal British Legion Festival of Remembrance at the Royal Albert Hall in London together.