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The royal is teaming up with husband Prince William and the former Great British Bake Off judge for the BBC Christmas one-off, which follows the trio "as they serve a festive feast to thank those who are spending their Christmas helping others."
And during the festive special, which airs on Monday, Kate, 37, admitted that her youngest is a fan of Berry, so much so that one of his first words was "Mary" as all her cookbooks in the kitchen are at his height and he recognises her face.
Honestly, this is too cute.
According to the Daily Mail, Kate tells Mary in the programme: "One of Louis' first words was 'Mary' because right at his height are all my cooking books in the kitchen bookshelf...
"And children are really fascinated by faces, and your faces are all over your cooking books and he would say 'That's Mary Berry'...so he would definitely recognise you if he saw you today."
So does that mean he's automatically a star baker then?
The royal couple welcomed their youngest son Louis in April 2018 and are also parents to Prince George, six, and Princess Charlotte, four.
Discussing the special with Mail on Sunday's You Magazine, Mary said it was nice to be around the royal couple and see their affection for one another.
She said: "It was just lovely observing [Will and Kate] for those three days.
"When they are together, he's constantly touching her arm and looking over at her smiling and she's the same with him. It was very sweet to see because it was so natural."
A Berry Royal Christmas airs on BBC One at 8:30pm.
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