This is why the royal family were laughing in Prince Charles’ birthday pictures

It was the shot we’d all been waiting for – the extended royal family all posing together in one gorgeous group portrait.

To mark the occasion of Prince Charles’ 70th birthday earlier this month, Kensington Palace released a series of photographs showing the Prince of Wales with his wife Camilla, his sons Princes William and Harry, their wives Kate and Meghan, and his grandchildren Prince George, Princess Charlotte and Prince Louis, all in one place for the very first time.

Getty Images

One of the pictures in the series, taken by the family’s photographer Chris Jackson, was a candid snap where everyone is seen breaking out into a fit of laughter – and now a source has revealed to US Weekly the adorable reason why.

According to the royal insider, the image came to be thanks to William and Kate’s Spanish nanny, Maria Teresa Turrion Borrallo, who was on the other side of the camera ‘making silly faces and waving to get their attention.’

‘Everyone burst into laughter at one point, making for a more relaxed photo,’ they explained to the magazine.

Getty Images

MORE: The hidden meaning behind Kate’s polka dot dress

According to US, the family photoshoot lasted just 15 minutes when it took place back in early September, and four-and-a-half month old Prince Louis was reportedly ‘so well behaved,’ and is ‘the most adorable, placid little boy you will ever meet’.

Maria has been working with the Cambridge family as a nanny since 2014, when Prince George was only 18 months old, and has since attended many official engagements with them, including the weddings of Kate’s sister Pippa Middleton and James Matthews, Prince Harry and Meghan, and Princess Eugenie and Jack Brooksbank.

‘Maria loves the children dearly,’ a source told PEOPLE magazine previously. ‘She can be firm and strict, but she is very loving and soft with them too.’