Princess Charlotte adds a personal touch to her school outfit

Princess Charlotte arrived at Thomas's Battersea for her first day of school on Thursday, wearing a pristine new school uniform.

But the young Royal added a little personal touch to the new look for her first day of "big school".

Attached to her new bag, was a pink sequins unicorn keychain hanging off the zipper.

The little accessory glimmered in the morning light, as Kate Middleton carried her four-year-old daughter's backpack onto the school grounds.

The commonly available kids keychain costs anywhere from $1.05 - $5.50 from a number of UK retailers.

Princess Charlotte was dropped off by both mum and dad, Prince William along with older brother Prince George, just after 8.15am (local time).

The family was greeted by head of the lower school, Helen Haslem, who shook hands with their newest Royal pupil.

A video shared by Kensington Palace shows William telling reporters his daughter was "very excited" to be starting school.

It was also a special moment for proud mum Kate Middleton, who missed out on taking Prince George for his first day of school, while pregnant with Prince Louis and suffering extreme morning sickness.

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Prince George, six, is returning for Year 2 at the school and will no doubt show his sister the ropes.

At school the young Royal will not be referred to as Princess, instead, she will go by the name Charlotte Cambridge, adopting her parents title as her surname.