Prince William's 'dirty' secret weapon for happy marriage to Princess Kate

The Prince and Princess of Wales have been together for more than 20 years - and now a royal expert has revealed the trait that is 'key' to their happy marriage

After more than a decade of marriage, Prince William and Princess Kate couldn't be happier. The couple have weathered a great deal together - including the heartbreak of Kate's recent cancer battle - but there is one thing that keeps their relationship firmly on track, according to an expert.

Christopher Andersen, author of 'The King', has said it's the couple's playful side that acts as their secret weapon – and it's something they're passing on to their three children.

He told Fox News Digital: "William once described Kate's sense of humour as 'naughty' and his own as 'dirty', and claimed that it was one of the most important things that drew them together. They've certainly cleaned up their act for the children's sake, but they can still make each other double over laughing."

The author continued: "William and Kate have also passed their wacky, slapstick, Monty Python-meets-Benny Hill sense of humour on to the children. And like all parents of young children, William and Kate find themselves refereeing when the kids fight over the TV remote, or when the inevitable teasing that goes on between siblings turns into the equally inevitable wrestling match."

Another thing the royal couple have in common is a competitive streak - although it seems Kate takes the crown. During an appearance on The Dog podcast, James Middleton admitted that the future King had found family games nights a bit too much.

"The Middletons are quite competitive and they love a game, don't they? And then you made poor William play, and he found it too competitive and actually used to make excuses," host Emily Dean noted.

He replied: "It was after family dinner, we would be sat there and the cards would come out, and [he would] perhaps see if Ella needed a walk or make an excuse to get down from the table. Racing demon is probably the most fast-paced, competitive one that we all play together."

James's beloved dog Ella passed away in January 2023 and his new book, Meet Ella: The Dog Who Saved My Life, is focused on their bond. In James's opinion, Ella was the perfect "excuse" for Prince William to escape playing cards and the royal actually looked forward to losing so he could go and "cuddle" her.

"Ella gives [William] a good excuse to escape the fiercely competitive nature of the Middleton family, which emerges every time we play our favourite fast-paced card game, racing demon," James wrote. "William flinches at our ruthless determination to win at all costs. He's delighted to be the first out, and when no longer compelled to take part, he slinks off to cuddle Ella.

"I think he'd prefer to absent himself from the game entirely. 'James, does Ella need a walk?’ he asks before we've even started dealing the cards," the Princess of Wales's younger brother added. "My sisters and I exchange a knowing glance: William, for all the competitive rigour of his military training, is happy to be a loser at cards."