The one activity Prince William won't do with the 'fiercely competitive' Middletons

Whilst Prince William has an exceptionally close bond with his in-laws, there is one activity he likes to skip when it comes to family get-togethers with the Middletons.

According to the Princess of Wales' brother, James Middleton, the future King used to use James' beloved therapy dog, Ella , as a way to get out of playing the Middletons' favourite card game: Racing Demon.

© Kensington Palace

The revelation was made in an excerpt of the entrepreneur's new book, Meet Ella: The Dog Who Saved My Life, shared with the Daily Mail. Ella meant an awful lot to James, who admits she saved his life during his battle with depression.

The dad-of-one wrote: "I know, too, that Ella gave him a good excuse to escape the fiercely competitive nature of the Middleton family, which emerged every time we played our favourite fast-paced card game, Racing Demon."

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He added: "'James, does Ella need a walk?' he'd ask before we’d even started dealing the cards. My sisters and I would exchange a knowing glance: William, for all the competitive rigour of his military training, was happy to be a loser at cards."

According to James, William was "smitten" with Ella from the moment they met. He wrote: "When he first encountered her as a tiny puppy at Bucklebury, he was smitten. He'd had a black Labrador, Widgeon, as a boy, and when Widgeon died, it left an empty space. I felt William was pining for a dog when Ella was around."

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Other incredible revelations in the book include James recounting the special moment Princess Charlotte, nine, and Prince George, 11 , met his now-wife, Alizée Thevenet.

After attending a wedding near his parents, Carole and Michael Middleton's home in Bucklebury, Berkshire, James and Alizée decided, on a whim, to stay the night at his childhood home.

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"We let ourselves in and tiptoed around in the dark, not wanting to wake anyone," he wrote, completely unaware that Prince William and Kate – along with their three children – were also staying for the weekend.

"It's George and Charlotte," he recalled after hearing the royal youngsters giggling from next door.

James gently hushed the children and took them downstairs. There, James found his sister Kate and brother-in-law William already having an early morning tea in the kitchen.

"I'm about to take a cup up to Alizée when she appears at the kitchen door," he added. "She has just got out of bed, her hair still tousled, and she is wearing one of my shirts. In situations like this, Alizée is wonderfully French. She does not panic or rush upstairs to get dressed.

"Instead, she just greets everyone warmly, as if it's not remotely unusual to be meeting her boyfriend's sister and brother-in-law for the first time while wearing only an oversized man's shirt."

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The royal children then started to ask "all kinds of cheeky questions at 100 miles per hour."

"'How come we weren't there when they went to bed? And who is this lady? Is she your girlfriend?'" recalled James. "(Cue giggles from both of them.)

"So I tell Charlotte and George, yes, she is my girlfriend and introduce her to them. Then we are all talking and laughing as if she has been part of the family for years."