Listing tennis, hockey and running among just a handful of her favourite pastimes, we’ve often wondered why we’ve never seen Kate Middleton taking part in a marathon.

After all, she’s regularly seen donning her trainers during public appearances to promote fitness and even had a go running on a track in Stratford this week, as part of an appearance for SportsAid.

The Duchess Of Cambridge Visits London Stadium To Meet The Parents And Guardians Of SportsAid Stars
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However, there’s one very understandable reason why we’ll never see the mother-of-three on the starting line of a marathon.

Last year, journalist and friend Bryony Gordon discussed her close relationship to the royals and the first time she met the Duchess of Cambridge during an appearance on ITV's Loose Women.

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After being introduced to the royal to discuss Heads Together at the sporting event, Gordon says she asked Kate if she’d be running the marathon.

‘Oh no, security and all that,’ Kate replied, according to Gordon.

In response, the author of Eat, Drink, Run said: ‘If I can do the marathon, you can.’

Meanwhile, Kate’s younger sister Pippa completed her The reason why you’ll never see Kate Middleton running a marathon.

week strength training plan for runners HELLO!:"I decided that a marathon was a “life box” that needed ticking and this year was my time – despite it being one of the toughest in the world, with temperatures rising to more than 30ºC, at an altitude of 5,550ft and with the possibility of bumping into lions or rhinos."

Pippa also completed the 2016 Great Wall Marathon in China, finishing with a time of 4:54:51 and a position as the 13th fastest female.

Related: 41 other celebrities you didn't know were marathoners

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Could Meghan Markle, or any of the other members of the Royal Family run a marathon?

According to reports in the press earlier this year, keen runner Meghan Markle, the Duchess of Sussex, has previously spoken about taking on a marathon, raising money for charity. Although it's not been confirmed, it's unlikely Meghan would be allowed to take part, for the same reasons Kate can't. That said, Princess Beatrice became the first member of the Royal Family to run the London Marathon in 2010, as part of a human caterpillar, so who knows!

From: ELLE UK