In pictures: Cambridges release image as UK's Prince Louis turns three

New photo of Prince Louis was taken by Duchess of Cambridge at Kensington Palace

Prince Louis, who is celebrating his third birthday, smiles before his first day of attending Willcocks Nursery School, at Kensington Palace in London. AP Photo/Duchess of Cambridge

A photo released by Kensington Palace of Prince Louis taken by his mother Catherine, the Duchess of Cambridge in 2020. Reuters/The Duchess of Cambridge

Prince Louis attends a special pantomime performance at London's Palladium Theatre with his father Prince William and mother Catherine, Duchess of Cambridge, along with his siblings Princess Charlotte and Prince George in December 2020. Getty Images

Prince Louis sits on the lap of his mother, Catherine, Duchess of Cambridge, during a pantomime at London's Palladium Theatre in December 2020. Getty Images

Prince Louis is held by his mother Catherine, Duchess of Cambridge, as the family takes part in a clap for NHS carers for BBC Children In Need in April 2020. Getty Images

Catherine, Duchess of Cambridge, holds Prince Louis while Princess Charlotte plays during the King Power Royal Charity Polo Match at Billingbear Polo Club in Wokingham in July 2019. Getty Images

Prince Louis is held by Queen Elizabeth, as she and Prince Philip pose with their great grandchildren. AFP

Prince William holds Prince Louis as Catherine, Duchess of Cambridge, laughs while on the balcony of Buckingham Palace to watch the Trooping the Colour, the Queen's annual birthday parade, in June 2019. Getty Images

Catherine, Duchess of Cambridge, and her son Prince Louis play in the Adam White and Andree Davies co-designed garden before the RHS Chelsea Flower Show in London in 2019. AP Photo

Catherine, Duchess of Cambridge, carries Prince Louis as they arrive for his christening service at St James's Palace in July 2018. Getty Images

Prince William and Catherine, Duchess of Cambridge, pose for photographers with their newborn baby boy Prince Louis outside the Lindo Wing of St Mary's Hospital in April 2018. Getty Images

Prince Louis was born on April 23, 2018. Getty Images

A crowd of media outside the Lindo Wing of St Mary's Hospital on the day Prince Louis was born. Getty Images

The Duke and Duchess of Cambridge's youngest son celebrates his third birthday on Friday, a day after the end of the royal family's official two-week period of mourning after the death of Prince Philip.

The royals released a new photo to mark the occasion, which shows a smiling Prince Louis perched on a bicycle on his first day at nursery this week.

The photo, taken by the Duchess of Cambridge in the grounds of Kensington Palace, shows Louis with a school bag strapped to his back on his first day at the Willcocks Nursery School.

The nursery is the same one attended by Louis' older sister Princess Charlotte, who turns six next month.

Prince George, the eldest of the three siblings, attended the Westacre Montessori School Nursery near the royal residence of Sandringham.

With Louis' first few years spent largely away from the public gaze, any sightings of him or his siblings are eagerly anticipated.

The duchess is a keen amateur photographer and a patron of the Royal Photographic Society.

Just last week, a photo of Louis with Prince Philip, Queen Elizabeth II and six other great-grandchildren was released as part of arrangements for the Duke of Edinburgh's funeral.

It was the first time Louis featured in an official portrait with the queen.

Last Christmas, his parents Prince William and Catherine released a family photo taken at Anmer Hall, on the queen's Sandringham estate in Norfolk. The image was used on the family’s Christmas card.

Louis Arthur Charles Windsor, born in St Mary’s Hospital, London, is fifth in line for the throne after his grandfather Prince Charles, his father, Prince William, and his siblings.

The first image released of him is from a photo call on the steps of St Mary’s when he was a few days old and in his mother’s arms.

Louis was left at home last weekend when the funeral service was held for Prince Philip.

Queen Elizabeth marked her 95th birthday on Wednesday while mourning her husband Philip.

See photos of the queen