Kate Middleton's response to Prince William running the London Marathon is hilarious

Oh Kate.

Does a day go by when Prince William and Kate Middleton don't give us couple goals?

During their tour of Cornwall the Duke and Duchess of Cambridge gave some seriously sweet life lessons whilst visiting a youth centre in Truro, showing off their nurturing sides that no doubt come from parenting Prince George and Princess Charlotte.

Of course, it's important to remember that Kate and Wills are just like the rest of us mere mortals at the end of the day. And like most couples, the two like a laugh at the others expense every now and then (remember when William called Kate a banana? Exactly).

Well, Kate got her own back yesterday after making a joke at the idea of her husband running in this year's London marathon.

The Duke and Duchess of Cambridge attended the Institute of Contemporary Arts yesterday in support of Heads Together, an organisation aiming to open up conversations around mental health.

Whilst there, William got chatting to Good Morning Britain journalist Sean Fletcher about his plans to run the London marathon at some point in the near future.

However, when Sean relayed William's plans to Kate she replied: 'I'll believe it when I see it.'

What a joker.

Personally, we'd love to see Wills running the marathon. And given that shorts are Prince George's signature style maybe William could turn to his son for some style advice before sporting the look himself?