Princess Charlotte's favourite joke proves she has a cheeky sense of humour

Prince William shared a rare insight into Princess Charlotte's super sweet sense of humour when he revealed her favourite 'knock knock' joke during his most recent royal engagement. 

The future King, who is first in the line of succession, laughed that he was going to "channel his inner Jack Whitehall" as he geared up to tell his daughter's go-to joke during his visit to a school in the West Midlands. 

Princess Charlotte is seemingly quite the joker as her father revealed that she's always cracking one particular joke to him - and he took inspiration from her when he was asked for his best "dad joke". 

After arriving at St Michael's Church of England High School to fulfil his promise to student Freddie Hadley to pay a visit to talk about mental health, William sat down with pupils to discuss their #AmIManlyEnough campaign. Freddie and other boys at the school set up the initiative last year to help fight the stigma surrounding male mental health. 

When asked to give the young teens a laugh, Prince William replied, "I am here with the gang talking about male mental health and I've been asked to produce a dad joke so I'm trying to channel Jack Whitehall because most of his jokes are pretty dad-like."

William, who lives at Adelaide Cottage near Windsor with the Wales family, continued, "I'm going to say a joke which is Charlotte's favourite joke, at the moment, which she keeps telling me."

"Knock knock," Prince William began, prompting the classic "Who's there?" response.  

"Interrupting cow," Prince William continued, interjecting with a quick "moo!" before the pupils could ask, "Interrupting cow, who?"

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As everyone giggled, William added, "That’s the one I hear a lot of at home at the moment," and joked, "That’s the greatest one I can think of that's clean and broadcastable."

The future King is known to share a special bond with Charlotte, who is his and the Princess of Wale's second-born child - and has a lovely nickname for her in the form of the word "mignonette" which means "small" or "delicate" in French.