The Duchess of Cambridge's Scathing One-Liner About Prince William Running a Marathon Is Priceless

(Image credit: getty images)

From laughing about her husband needing a toupee made from alpaca hair to joking that she think he acts like a teenager, the Duchess of Cambridge has given us some hilarious zingers about the Duke of Cambridge.

However, this could be her best yet.

Sleeve, Facial expression, Style, Fashion, Long hair, Day dress, Trunk, Makeover, Design, Layered hair,

(Image credit: getty images)

On Tuesday, the royal couple and Prince Harry attended an event to highlight their mental health charity Heads Together, where Good Morning Britain's Sean Fletcher revealed Kate had shared exactly what she thought of her husband's desire to run a marathon one day.

Fletcher told reporters: 'I chatted to Prince William, and he has promised that he will run a marathon in Kenya sometime.'

Clothing, Coat, Smile, Trousers, Dress shirt, Shirt, Collar, Outerwear, Suit, Formal wear,

(Image credit: getty images)

He added: "Then I spoke to Kate and she said, 'I'll believe it when I see it.'"

It's not entirely a surprise that Kate likes to joke about her husband's sporting prowess (despite him being an incredibly skilled polo player) as the pair have spoken about their healthy competitive sides on several occasions.

Coat, Suit, Formal wear, Interaction, Tie, Cap, Conversation, Blazer, Hair accessory, White-collar worker,

(Image credit: getty images)

In 2014, the pair went out on yachts during their royal tour of Auckland, New Zealand where they separately competed in a race, according to E!.

Before the competition, Kate jokingly told William, "Take care!" before patting him on the back.

"Yeah, see you later," he replied, before his wife eventually took first place.

Kate, 1. William, 0.

Follow Marie Claire on Facebook for the latest celeb news, beauty tips, fascinating reads, livestream video, and more.