He's adored by royal fans around the world for his expressive behaviour - and Prince Louis didn't disappoint as he attended the Trooping the Colour ceremony today.
During just one of his many animated displays, the young prince was caught on camera scrunching up his face, while Kate, 42, appeared to crouch down to talk with her son on a balcony on Horse Guards Parade.
The Prince and Princess of Wales' youngest child, was also captured yawning at the London event, which usually consists of more than 1,400 parading soldiers, 200 horses, 400 musicians and a flyover of 70 aircraft.
Seemingly not occupied enough by the parade, at one point, the cheeky six-year-old was even caught tugging on the cord for the blinds as he chatted to his mother.
Louis, who was wearing a double breasted blazer, a pair of shorts, a crisp shirt and a tie, could not hide his facial expressions - much to the enjoyment of royal fans.
This is the adorable moment Prince Louis was left unimpressed by the Trooping the Colour ceremony
The Prince and Princess of Wales ' youngest child, was also captured yawning at the event, which usually consists of more than 1,400 parading soldiers, 200 horses, 400 musicians and a flyover of 70 aircraft
He even attempted to try and open the window on the balcony next to the Duchess of Edinburgh, gripping the frame as he tried to pull it up.
And the Prince looked less than impressed during the ride, knitting his brows together at points as he stared out of the window, open-mouthed.
Prince William took part in the parade on horseback, while his children appeared alongside their mother in a carriage before all the family joined one another on the Buckingham Palace balcony.
The flypast began as senior royals came out onto the balcony - with Charles and Camilla followed by Kate and William and their children George, Charlotte and Louis. Kate then leant over to speak to Charles, who laughed at something she said.
They were joined by the Duke and Duchess of Edinburgh, with the family smiling and waving to crowds before standing proudly as the national anthem was played.
Kate's appearance had been in doubt after she missed the final Trooping rehearsal last weekend, with confirmation that she would attend only given at 6pm yesterday.
But with the King also suffering from cancer, today's spectacle of military pomp and pageantry became a symbolic statement by the monarchy after much uncertainty.
Prince Louis wipes his eye while standing on the Buckingham Palace balcony in London today
Members of the Royal Family watch the flypast from the Buckingham Palace balcony today
The Prince and Princess of Wales with their children and the King on the balcony of Buckingham Palace, London, to view the flypast following the Trooping the Colour ceremony
Prince William and Kate attend Trooping the Colour at Buckingham Palace in London today
William and Kate smile at each other on the Buckingham Palace balcony in London today
Scotland Yard had a 'substantial' policing operation in place, with anti-monarchy group Republic allowed to protest but banned from using amplified sound.
Hundreds of Metropolitan Police officers were deployed on the ceremonial route to ensure the safety and security of those watching, with tens of thousands gathered.
Earlier, the 42-year-old Princess of Wales beamed and waved as she and her three children, Prince George, Princess Charlotte and Prince Louis, were cheered by crowds on The Mall in a carriage procession for the Trooping the Colour ceremony.
Kate was surrounded by other members of the family - with her husband Prince William , Colonel of the Welsh Guards, on horseback, along with Princess Anne , Colonel of the Blues and Royals, and Prince Edward , Colonel of the Scots Guards.
After spending much of the year coming to terms with the diagnosis and receiving ongoing chemotherapy, Kate looked relaxed as she travelled along one of London's most famous thoroughfares with her family in the glass state coach.
The family were first seen arriving at Buckingham Palace in a car at 10am, with George sitting between Kate and William, and Charlotte and Louis opposite.
King Charles III also rode in a carriage with Queen Camilla, a departure from last year because of his illness, and he inspected the officers and guardsmen on Horse Guards Parade in Whitehall from the coach rather than from a horse.
Ahead of her appearance, the Princess penned a moving personal message thanking the public for their support over her cancer diagnosis and revealing she is looking forward to attending the traditional ceremonial day.
Prince Louis is pictured trying to open a window on a balcony on Horse Guards Parade next to the Duchess of Edinburgh
Prince Louis, known for his cheeky antics, tries to open a window during Trooping the Colour today
Prince Louis, known for stealing the limelight at royal events, pulls a face at Trooping the Colour today
Prince Louis looked less than impressed with the event as he stepped out with his family
Prince Louis points to something during the Trooping the Colour event
Beaming Princess Charlotte couldn't help but smile as she appeared alongside her brother Prince George at today's Trooping the Colour
Kate beams as she accompanies her children in a carriage during today's procession (pictured L-R: Kate, Prince Louis, Princess Charlotte)
Back in March, the Princess disclosed she was undergoing 'preventative chemotherapy' for an undisclosed form of the disease says her treatment is on going and will be for several months to come.
While she will not be returning to public duties full-time, she revealed that she does now feel well enough, however, to undertake a small number of public engagements in the coming months.
To mark the news Kensington Palace have also released a stunning new portrait of the princess taken at Windsor this week by Matt Porteous showing her looking well and in a reflective mood.
In her message the Princess says she has been 'blown away' by all the kind messages of support and encouragement over the last couple of months.
'It really has made the world of difference to William and me and has helped us both through some of the harder times,' she wrote.
Kate arrives at Horse Guards Parade today as Trooping the Colour takes place
The Princess of Wales speaks with Prince Louis as they watch Trooping the Colour today
Prince Louis looks on during Trooping the Colour in London this morning
Movingly she reveals she is making 'good progress', but adds: As anyone going through chemotherapy will know, there are good days and bad days. On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well.'
She added: 'My treatment is ongoing and will be for a few more months. On the days I feel well enough, it is a joy to engage with school life, spend personal time on the things that give me energy and positivity, as well as starting to do a little work from home.
'I'm looking forward to attending The King's Birthday Parade this weekend with my family and hope to join a few public engagements over the summer, but equally knowing I am not out of the woods yet.
'I am learning how to be patient, especially with uncertainty. Taking each day as it comes, listening to my body, and allowing myself to take this much needed time to heal.
Thank you so much for your continued understanding, and to all of you who have so bravely shared your stories with me.'
The Princess first announced that she had cancer on March 22.
In a hugely moving video statement, recorded at Windsor, she revealed that she had been diagnosed following serious abdominal surgery in January and was already undergoing 'preventative' chemotherapy.
In a deeply personal, unprecedented and emotional video message filmed just two days earlier, Catherine revealed the news had come as a 'huge shock' and that she and William 'have been doing everything we can to process and manage this privately for the sake of our young family'.
'It has taken us time to explain everything to George, Charlotte and Louis in a way that is appropriate for them, and to reassure them that I am going to be ok,' she said.
'As I have said to them; I am well and getting stronger every day by focusing on the things that will help me heal; in my mind, body and spirits. Having William by my side is a great source of comfort and reassurance too. As is the love, support and kindness that has been shown by so many of you. It means so much to us both.'
Kensington Palace said at the time that it would not be sharing details of what kind of cancer the princess has, or what stage of cancer it is and asked people not to speculate.
At the time of her abdominal surgery in January, Kensington Palace said that it was non-cancerous. They confirmed again in March that is the case and that no tests had confirmed the presence of cancer. However post-operative tests subsequently found that cancer 'had been present'.
A week ago, the royal apologised for missing out on a key rehearsal for the event, writing a letter to the Irish Guards, saying: 'I hope I am able to represent you all very soon'.
