In a moving tribute to the Queen, the Prince of Wales highlighted the 20-year friendship his late grandmother shared with his wife.
He said he felt "incredibly grateful" for the wisdom he gained from the late Monarch and the "guidance and support" she offered Kate.
The two women were said to have "very similar personalities" as well as shared interests including photography and animals.
And Kate has fond memories of her first meeting with the Queen, despite the historic day happening in quite unusual circumstances.
They were first introduced at Peter Phillips' wedding to his now ex-wife Autumn, however William wasn't actually there. Kate attended solo as William was in Kenya attending his ex-girlfriend Jecca Craig's wedding.
Recalling the day during her engagement interview, Kate said: "Well I first met her at Peter and Autumn’s wedding. And again, it was in amongst a lot of other guests and she was very friendly."
William added: “She’s very welcoming. She knew it was a big day and everything was going on with Peter and Autumn were there and things and she’d wanted to meet Kate for a while so it was very nice of her to come over and say hello.”
At the time, The Telegraph reported that William's decision to skip his cousin's royal wedding was not intended as a snub. A source said: "Prince William is going to be out of the country this weekend on a long-standing prior engagement. It is an unfortunate clash but he spoke to his cousin Peter and he is fine with the situation. His girlfriend will be going in his absence."
Kate has shared a handful of stories about her personal interactions with the Queen over the years, including her first Christmas with the family.
Speaking in the ITV documentary Our Queen at Ninety, she said: "She really cares. I can remember being at Sandringham, for the first time, at Christmas. And I was worried what to give the Queen as her Christmas present.
"I was thinking, 'Gosh, what should I give her?' I thought back to what I would give my own grandparents. And I thought, 'I'll make her something.' Which could have gone horribly wrong. But I decided to make my granny's recipe of chutney."
Kate added: "I was slightly worried about it, but I noticed the next day that it was on the table. I think such a simple gesture went such a long way for me and I've noticed since she's done that on lots of occasions and I think it just shows her thoughtfulness, really, and her care in looking after everybody."
Kate looked emotional as she joined William, Prince Harry and Meghan Markle to view the floral tributes in Windsor yesterday.
She was overheard telling a well-wisher about breaking the news to her children George, Charlotte and Louis.
She told Banita Ranow, 28, who was part of the crowd gathered on the Long Walk: “Louis said at least Grannie is with Great Grandpa now.”
Ms Ranow said Kate was “welling up” as she spoke to them.
You can leave your tributes to Queen Elizabeth II here.
