The American nickname George and Charlotte have for Prince William

If you were to ever bump into Prince William, chances are you'd go to great lengths to ensure you address him correctly – which, for most of us, would involve calling him "Your Royal Highness".

But for his children, Prince George, 5, Princess Charlotte, 3 and Prince Louis, 7 months, there's no such formality.

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And this week, Duchess of Cambridge Kate Middleton revealed exactly what their children call him.

During a visit to Leicester, Middleton apparently told Leicester City season ticket holder Fiona Sturgess that they call him "Pops".

The Duke and Duchess of Cambridge with their children (PA Wire/PA Images)

"Kate said that William was playing football with the children last night and one of them said, I think it was George, ‘Are you playing football tomorrow, Pops?’," she told reporters.

(Getty Images)

It's not the only Royal nickname – in The Queen at Ninety, ITV's anniversary broadcast on the Queen's reign, Kate Middleton also revealed that her children call the monarch "Gan Gan".

Their nickname for Prince Charles is "Grandpa Wales."