Prince George, Princess Charlotte and Prince Louis are all smiles as they arrive for their first day at school

The big day is finally here!

Four-year-old Prince Louis has arrived for his first day at the co-educational private Lambrook School in Ascot, Berkshire.

Joined by his parents, the Duke and Duchess of Cambridge, his nine-year-old brother, Prince George, and his seven-year-old sister, Princess Charlotte, for the momentous day, the young royal made a charming arrival in his brand new uniform.

Photographed making their way into the school, Kate could be seen holding hands with George and Louis, while William walked hand-in-hand with Charlotte before they confidently greeted the school's headmaster, Jonathan Perry, with a firm handshake.

"Welcome to Lambrook," the headmaster told the children. "It's lovely to have you with us. We're very excited for the year ahead."

He then asked them: "Are you excited?"

To which all three piped up: "Yes!"

It is the first time all three siblings have attended school together, with Louis starting his education in pre-prep and his older siblings joining the prep as new starters.

The Cambridges enrolled in the prestigious school after they moved out of London to Windsor to be closer to the Queen who now lives permanently at Windsor Castle.

Lambrook - which says it gives its pupils "feathers to fly" and a "delicious sense of freedom" - will cost the royals an eye-watering £53,000 a year.

Fees cost £4,389 a term for Prince Louis, £6,448 per term for Charlotte and £6,999 per term for George.

Lambrook boasts of "first-class teaching and superb facilities" which include a 25-metre swimming pool, a nine-hole golf course set in 52 acres of idyllic Berkshire countryside, an astroturf, hard courts, a squash court, cricket and other sports pitches.

It also has a Diamond Jubilee performing arts studio, dance studio and sports hall, and a new £6 million Queen's Building for ICT and academic learning.