Royal fans have said Prince Louis is growing up fast as he donned blue shorts, a shirt with a tie and an elegant jacket to join other members of the Royal Family for the Easter Sunday service this morning.
The four-year-old, who is celebrating his fifth birthday on April 23, arrived at St George's Chapel in Windsor clutching his mum Kate's hand and walked next to his sister Princess Charlotte as they headed to church.
After photos of royals emerged, fans were quick to share their reaction on social media, with many describing Prince Louis, Princess Charlotte and Prince George as "beautiful".
Some people pointed out that Louis is growing up fast and others said he is likely to become a tall man in the future.
Others even branded Louis "Boss Baby" while several people pointed out how elegant he looked as he arrived at church.
Louis is known for his cheeky behaviour, for example during the Sunday pageant organised during the late Queen's Platinum Jubilee last year, he was seen trying to cover his mum's mouth and blowing raspberries.
He also appeared to get a warning from Mike Tindall, who sat behind the young prince who was also snapped putting his fingers in his ears and throwing a cushion around.
Louis was also spotted pointing at Kate making her laugh, wriggling around in his seat, pointing out the things he had spotted in the parade and putting his hands over his eyes.
Today, after Louis joined other royals at church, a person tweeted: "Prince Louis is on his best behaviour and I don't like it."
Another wrote: "Prince Louis growing up so fast."
The Prince and Princess of Wales were described as "a lovely relaxed family" by another Twitter user who said Kate's red nail polish looked good on her this morning.
Senior royals including King Charles and Camilla, Queen Consort, were out in force at St George's Chapel on the grounds of the Berkshire castle for the traditional Easter Day Mattins.
Zara and Mike Tindall and Princess Beatrice with her husband Edoardo Mapelli Mozzi were pictured arriving at church with their family.
Prince Andrew also made a rare appearance, walking just behind the King by his sister Princess Anne's side.
Prince Edward, Duke of Edinburgh, and his wife Sophie, Duchess of Edinburgh, were also seen arriving at church with their son James, Earl of Wessex.
Princess Eugenie and her husband Jack Brooksbank, who are expecting their second child this summer, also attended the church service with their family.
All three of Prince William and Kate's children will play starring roles in King Charles' coronation, leaked plans show.
Prince George, Princess Charlotte and Prince Louis will join the monarch and the Queen Consort Camilla as they leave Westminster Abbey at the end of the ceremony on May 6.
The procession back to Buckingham Palace is reportedly set to be a third of the size of that at Queen Elizabeth's coronation in 1953.
However, the palace has insisted it would be "amazing in both scale and splendour".
