Prince Louis’ secret hidden message to Kate Middleton’s mum and dad revealed after card is spotted

Prince Louis, the youngest son of the Prince and Princess of Wales, wrote a heartwarming note to his grandparents last week.

Louis was in attendance for the Together at Christmas carol service on 6 December along with his sister, Princess Charlotte, 9, and Prince George, 11.

Part of the service is a 'Kindness Tree,' which is set up outside Westminster Abbey, on which many guests leave notes.

It has emerged that Prince Louis left a note addressed to his grandparents, the parents of his mum Kate - Carole and Michael Middleton.

Prince Louis left a note addressed to his grandparents (Max Mumby/Indigo/Getty Images)

Louis' sweet note read: "Thank you to Granny and Grandpa because they have played games with me."

A source previously told People: "Her [Kate's] parents are an enduring factor in the upbringing of their grandchildren."

Following Kate's diagnosis of cancer and rounds of chemotherapy that resulted in the Princess of Wales being given the all clear, it was reported that her parents, as well as her sister Pippa and brother James, had been on hand to help out.

Another source added: "This is about supporting her and her feeling supported. It is a joint effort. She doesn’t feel isolated at all."

Upon Kate's status of being cancer free, she shared a video in which her parents appeared, alongside a statement.

The Together at Christmas carol service took place on 6 December (AARON CHOWN/POOL/AFP via Getty Images)

She said: "The last nine months have been incredibly tough for us as a family. Life as you know it can change in an instant and we have had to find a way to navigate the stormy waters and road unknown.

"The cancer journey is complex, scary and unpredictable for everyone, especially those closest to you.

"With humility, it also brings you face to face with your own vulnerabilities in a way you have never considered before, and with that, a new perspective on everything. This time has above all reminded William and me to reflect and be grateful for the simple yet important things in life, which so many of us often take for granted. Of simply loving and being loved."

She added: "Although I have finished chemotherapy, my path to healing and full recovery is long and I must continue to take each day as it comes," she said, hinting at what's ahead.

"I am however looking forward to being back at work and undertaking a few more public engagements in the coming months when I can. Despite all that has gone before, I enter this new phase of recovery with a renewed sense of hope and appreciation of life."