First there was their affectionate hug. Then it was revealed that when Michelle Obama was in London in an unofficial capacity, she and her daughters, Malia and Sasha were given a rare private three-hour tour of Buckingham Palace, including an audience with the Queen last week.
No photographers were present to capture the unprecedented meeting but a royal sources spoke of the "personal warmth between the two of them".
"Clearly the queen, the Duke of Edinburgh and the Obamas got on very well at the G20 summit and mention was made then that they should keep in touch and they have done," added the source.
The permission for the tour was granted by the 83-year-old monarch as a treat for Sasha who turned eight last week.
According to sources, the two ladies have bonded over a love of gardening, the countryside and fashion.
On being introduced to the US First Lady in April, the royal matriarch put an arm warmly round her, in a spontaneous display of friendliness. She was later heard telling her American visitor: "Now we have met, would you please keep in touch."
The revelations about their second encounter came as the Queen and her entire family was enjoying the pomp and pageantry of the Trooping The Colour.
Marking her official birthday – her actual one is on April 21, but the ceremony is always in June because of the warmer weather - the centuries-old tradition involves a fly-past over the Palace balcony and a magnificent procession of hundreds of soldiers down the Mall.