Kate Middleton is Prince William's number one support system, but when it comes to the Prince running a marathon, she needs a little proof before cheering for him from the sidelines.
During a previous outing with William and Prince Harry in support of their Heads Together organisation at the Institute of Contemporary Art in London, William shared with one of the attendees his promise to run a marathon in Kenya. "I chatted to Prince William, and he has promised that he will run a marathon in Kenya sometime," Good Morning Britain's Sean Fletcher shared.
SEE: Kate Middleton will never run the marathon for this reason
WATCH: Royals at the marathon
When Sean, who went on to participate in the London Marathon in support of his son's diagnosis with Obsessive-Compulsive Disorder (OCD), told Duchess Kate about her husband's news, Prince George, Princess Charlotte and Prince Louis' mum offered up the hilarious response: "I’ll believe it when I see it."
Sean went on to open up about his time with William: “This is all very new to me — I’m learning very fast because of my son’s situation. William’s understanding was incredible, but also his sympathy and empathy with me. He asked me lots of questions. I’ve never met him before, but he’s such a warm man. Like two dads talking together.”
SEE: Pippa Middleton talks to HELLO! about completing her first marathon
RELATED: Royals in activewear: Kate Middleton, Princess Beatrice, Meghan Markle and Co
The Duke and Duchess of Cambridge and Prince Harry supporting runners at the London Marathon in 2017
Kate, meanwhile, has previously revealed she will never run the marathon, and her reason likely applies to William, too, despite his intentions to run one.
During an appearance on Loose Women with author Bryony Gordon, Bryony asked the mother-of-three if she would be running the marathon, to which Kate answered: "Oh no, security and all that."
It makes sense - Kate and Will would both likely be inundated with fans, so we doubt we'll see either crossing the finishing line anytime soon.
Make sure you never miss a ROYAL story! Sign up to our newsletter to get all of our celebrity, royal and lifestyle news delivered directly to your inbox.