Princess of Wales reveals secret she asked Prince Louis to keep from big sister Princess Charlotte

Kate entrusted Louis with a surprise for Charlotte
Kate entrusted Louis with a surprise for Charlotte (Getty)

The Princess of Wales entrusted her son Prince Louis to keep a surprise for Princess Charlotte – and the young royal kept to his word!

Arriving ahead of her family at her annual Together at Christmas concert on Friday, Kate, 42, spoke with celebrity guests and performers inside Westminster Abbey.

While seeming to talk about the soloists from the Royal Ballet who performed during the service, Kate told singer Paloma Faith that she had enlisted Louis, six, to keep it a surprise for her daughter Charlotte, nine.

Watch the moment in the video below…

Kate said of Louis: "He has kept the secret for, what, nearly two weeks now."

"Very challenging," Paloma agreed.

“For a six-year-old," replied Kate. "And then this morning he said 'Mummy, please can I tell her – I'm bursting'. I did drop off and he really wanted to tell her. I think - hopefully – he's kept it."

The children are growing up fast
The children are growing up fast (Getty)

Charlotte later lit up as she saw the ballet dancers during the service, suggesting that her younger brother had been good to his word.

The Princess has inherited her late grandmother Princess Diana's love of dance and began taking lessons from a young age.

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Kate has also previously taken Charlotte on trips to watch the Royal Ballet at the Royal Opera House.

William, Kate and children singing at concert
William, Kate and children singing at concert (Getty)

The Wales children were smartly dressed in hues of navy and burgundy as they arrived at the Abbey with their father, Prince William.

The family were last seen altogether publicly at the King's birthday parade, Trooping the Colour, in June.

George, Charlotte and Louis also placed their own notes on the Kindness Tree, where guests were asked to place a dedication to someone who has supported them throughout the year.

Little Louis' handwritten note was dedicated to Kate's parents, Carole and Michael Middleton, who also attended the service.

It read: "Thank you to granny and grandpa because they have played games with me."