"The Queen is on cloud nine at the moment and wanted to share her happiness with her hard-working staff, so the obvious thing to do was to get out the champers," a courtier told The Express.
"Everyone was in a fantastic mood and we all toasted the baby, the parents and the Queen," added another member of staff. "It was a fabulous gesture of her and everyone appreciated it. Everyone is so happy for the royals and especially the Queen. We have never seen her looking so happy and content."
At Buckingham Palace, Windsor Castle and Holyrood Palace in Edinburgh staff were told by invitation that could "enjoy a glass of champagne to celebrate the royal birth".
Royal aides at Buckingham Palace celebrated Prince George's birth in the dining room between 11:30am and 1:30pm, those at Windsor Castle assembled in The Undercroft and staff at one of the Queen's Scottish residences, Holyrood, gathered in Abbey Strand.
The Queen has now left Buckingham Palace for Balmoral where she will spend the next couple of months enjoying her summer holiday.
Prince Philip, the Duke and Duchess of Cambridge and, of course, Prince George are all expected to join the sovereign at her retreat in the Highlands, as are Prince Andrew, Princess Beatrice and Princess Eugenie.