Princess Charlotte is "so excited" to start school next week

It's hard to believe it's been four years since we caught our first glimpse of Princess Charlotte swaddled in her mum's arms as she left hospital for the first time.

It's even harder to believe the second child of Prince William and Kate Middleton will be lacing up her 'big school' shoes in a matter of days.

On September 5, the princess will attend her first day of school at Thomas' Battersea, where she'll ditch her royal title and be known as Charlotte Cambridge.

She'll be joined there by her older brother Prince George, five, who'll be starting his third year at the London private school.

A source tells People magazine the princess is "so excited" to follow in her brother's footsteps.

"She can't wait to be with George at big school ... They are close in age, and they spend so much time together," they say.

It'll be an especially happy reunion, given how she reacted to George starting school in 2017.

"Charlotte cried when he left, but she's gradually become used to him not being around in the day," a source told Life and Style magazine at the time.

LISTEN: The Windsors podcast takes a look at the life of Catherine, Duchess of Cambridge. (Post continues.)

The princess' own schooling life began in January 2018, when she started at Willcocks Nursery School near Hyde Park.

As has become tradition for the Cambridge family, the milestone was marked by the release of two sweet photos of Charlotte taken by her mum, Kate.

We're likely to see more photos and maybe even some footage when Charlotte takes her first steps into Thomas' next week.

When Prince George started school, the world swooned over the sweet photos of the solemn-faced future king walking through the gates hand-in-hand with his father.

The Duchess was unable to join them, as she was in the early stages of her pregnancy with Prince Louis and suffering from hyperemesis gravidarum, or 'severe morning sickness'.

The royal parents are likely to continue their habit of doing the school run; they're often sighted at the gates of Thomas' Battersea with the other mums and dads.

Kate even dropped George off to school the day after she welcomed Prince George in April 2018.

As a former royal protection officer told 9Honey earlier this year, the royal school run is just as carefully orchestrated as any outing from a security perspective.

"There is still a large protection package attached to that particular movement, like taking the children to school, but it is dealt with in a different way," Simon Morgan explained.

"There's still the same level of planning, the same level of scrutiny, and quite importantly, the contingency planning from the protection officer's perspective as to what is an everyday occurrence across the world of a parent taking a child to school."

The return to school comes after a busy summer holiday for the Cambridges.

The family of five enjoyed some time in the Carribbean island of Mustique before heading to the Balmoral estate in Scotland to enjoy the warmer weather with the Queen.