Queen Elizabeth and Paddington the Bear have tea

Queen Elizabeth and Paddington Bear

| Credit: Buckingham Palace/Studio Canal/BBC Studios/Heyday Films via Getty

Even 70 years into her reign, Queen Elizabeth still has a few surprises up her sleeve.

Although the Queen, 96, didn't attend the Platinum Party at the Palace on Saturday night, she did open up the event with a fun pre-recorded sketch featuring another British icon: Paddington Bear. The hilarious skit featured the monarch hosting the beloved character for tea...and revealing what she keeps in her trusty handbag — a marmalade sandwich!

Buckingham Palace isn't commenting on the clip as they don't "want to de-mystify it," one royal source says, "and take away the magic."

But PEOPLE has learned that the video was filmed in March at Windsor Castle, with Paddington added later by CGI techniques. It's likely that a staff or crew member sat opposite the monarch during filming to help her.

For more on the Queen's Platinum Jubilee, listen below to our daily podcast PEOPLE Every Day.

The surprise was kept top secret — so much so that even members of the royal family had no idea about it until they were watching it open up Saturday's star-studded concert. Prince George and Princess Charlotte were clearly amazed, smiling and gasping as they watched their great-grandmother's interactions with Paddington onscreen. (Prince Charles, however, may have been clued in — his speech on Saturday did reference a marmalade sandwich.)