While visiting Bletchley Park on Tuesday, Kate was talking to a bunch of women and revealed her one-year-old son has been getting up to some mischief of late and likes to keep his parents on their toes.
The mother-of-three told one lady: "I turned around the other day and he was at the top of the slide – I had no idea!"
Kate later went on to accept some beautiful gifts for her children as well as for her new nephew, Archie Harrison, who was born last Monday.
She was given a squirrel, fox, owl and rabbit for Prince George, Princess Charlotte, Prince Louis and the Duke and Duchess of Sussex's baby Archie.
"They love wild animals. They will look after these," she said.
WATCH! Compare Baby Sussex's Big Debut with His Royal Cousins — George, Charlotte and Louis!