The Duchess of Cambridge has released a photograph of a smiling Princess Charlotte to mark her sixth birthday.

Princess Charlotte (c) Instagram

Princess Charlotte (c) Instagram

The young royal - who is fourth in line to the throne - celebrates her birthday on Sunday (02.05.21) and the picture, taken by the duchess, shows Charlotte looking happy ahead of her big day.

In the image, Charlotte is wearing a blue short-sleeved dress with a floral design.

Charlotte and her brothers Prince George, seven, and Prince Louis, three, also recently featured in a video to mark their parents' 10th wedding anniversary.

In the clip, the royals were seen at a beach and toasting marshmallows near Anmer Hall, their family home in Norfolk.

Meanwhile, Prince William - who married the duchess at Westminster Abbey in 2011 - recently joined a social media boycott in response to racism within soccer.

The 38-year-old royal - who became the President of England's Football Association in May 2006 - announced he was joining the "entire football community” in going silent on social media to raise awareness for "the sustained abuse received online by players and many others in the football community".

The prince - who is an avid fan of the sport - wrote on Twitter: "As President of the FA I join the entire football community in the social media boycott this weekend."

He also posted a picture of his tweet on Instagram alongside a caption which explained the blackout in more detail.

The caption read: "This weekend we join the football community in the UK in uniting for a social media boycott from 3pm on Friday 30 April to 11.59pm on Monday 3 May, in response to the sustained abuse received online by players and many others in the football community."