The Princess of Wales today made a triumphant return to public life amid her cancer treatment, joining the Royal Family to celebrate the King’s official birthday.

Kate beamed and waved as she and her three children, Prince George, Princess Charlotte and Prince Louis, were cheered by crowds in The Mall after leaving Buckingham Palace in a carriage procession for the Trooping the Colour ceremony.

After spending much of the year coming to terms with the diagnosis and receiving ongoing chemotherapy, the future queen looked relaxed as she travelled along one of London’s most famous thoroughfares with her family in the glass state coach.

Her 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, the spectacle of military pomp and pageantry became a symbolic statement by the monarchy after much uncertainty.

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.

The Princess of Wales leaves Buckingham Palace during Trooping the Colour in London today

Louis steals the show: Royal left unimpressed by Trooping the Colour

Moment Princess Charlotte appears to tell Louis to stop dancing

Kate with Prince George, Prince Louis and Princess Charlotte in the rain this afternoon

Earlier, the family were seen arriving at Buckingham Palace in a car at 10am, with George sitting between Kate and Prince William , and Charlotte and Louis opposite.

At 1pm, she is set to gather with King Charles and Queen Camilla , her husband and other Royal Family members on Buckingham Palace’s balcony for the RAF flypast.

Scotland Yard has a ‘substantial’ policing operation for the event, 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.

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.

Moment Kate smiles alongside three children in horse-drawn carriage

Kate steps off horse-drawn carriage alongside three children

King Charles and Queen Camilla attend Trooping the Colour in London today

Kate was greeted by a sea of faces as the royal party turned from The Mall into Horse Guards Parade, with the Duke and Duchess of Gloucester and Vice Admiral Sir Tim Laurence together in a carriage, while the Duchess of Edinburgh travelled in a coach with her daughter Lady Louise Mountbatten-Windsor and the Duke of Kent.

The royal party were in the midst of a sovereign’s mounted escort, formed by troops from the Household Cavalry’s Life Guards and Blues and Royals.

In the rear rank was Tennyson, one of the five horses injured when they ran through the streets of London after being spooked by construction noise.

In a change from last year, Kate did not join senior family members on a dais, but watched the spectacle from the Duke of Wellington’s former office with her children.

Kate stood beside her children as the regiments, in red ceremonial dress, continued to parade. She could be seen whispering in the ear of Charlotte as the band played.

‘All eyes will be on Kate’ at Trooping the Colour parade

The Princess of Wales, Prince George, Princess Charlotte and Prince Louis in London today

Louis, six, was watching the parade intently until his attention turned to what appeared to be a blind cord in the building, and he was also seen yawning.

In addition, Louis could be seen dancing along during the quick march of the Scots Guards to Highland Laddie.

The royal procession then moved back to Buckingham Palace just as heavy rain began falling in central London.

The King and Queen were protected from the downpour in their carriage. George, Charlotte and Louis also stayed dry, in a carriage with Kate.

Charles is Colonel in Chief of the regiments of the Household Division which include the Life Guards, Blues and Royals and all five regiments of Foot Guards – the Welsh, Scots, Irish, Coldstream and Grenadier – on parade for the official birthday, alongside the mounted Band of the Household Cavalry and the massed Foot Guards bands.

The King was seen waving a gloved hand to the crowds gathered to watch the procession. The Queen, wearing a large brimmed hat and seated to his left, was also seen waving.

The military spectacle, also known as the Birthday Parade is a gift from the Household Division, and Charles first attended in 1951, aged three, riding in a carriage with his grandmother, the Queen Mother, and aunt, Princess Margaret, and first rode as Colonel of the Welsh Guards in 1975.

George, Charlotte and Louis wait for Kate to step down from carriage

The Princess of Wales leaves Buckingham Palace during Trooping the Colour in London today

Trooping the Colour is a social as well as a ceremonial occasion and the stands overlooking the parade ground were filled with about 8,000 spouses, girlfriends and parents of the guardsmen and officers on parade.

It featured more than 1,250 soldiers, and hundreds of Guardsmen were lined up on the parade ground waiting to be inspected by the King from his carriage with Camilla, Colonel of the Grenadier Guards, and joined by the mounted royal Colonels.

The colour, or regimental flag, that will be trooped will be the King’s Colour of number 9 company, Irish Guards.

When the royal carriages finally came to a stop Louis was the first to leave, followed by his elder brother George and sister Charlotte.

Finally, Kate stepped down wearing wearing a Jenny Packham dress, hat by Philip Treacy and the Irish Guards Regimental Brooch, as she is the regiment’s Colonel.

Crowds of people gathered outside Buckingham Palace this morning, with many holding Union flags.

‘There are good days and bad days’: Kate’s statement in full

Here is the Princess of Wales’ statement on her cancer treatment and summer plans, including Trooping the Colour, in full:

‘I have 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.

‘I am making good progress, but 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.

‘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.’

Jane Ing, 61, said she had travelled from Yorkshire with her husband and a friend to witness the royal procession through The Mall ahead of the ceremony.

She said: ‘The ceremony is part of our heritage. It’s an iconic parade and exhibition of our royal family that we should be proud about and come to support.’

She added it was ‘lovely’ that Kate announced she will be in attendance.

Political artist Kaya Mar was among spectators gathered to watch the royal procession down The Mall.

The 67-year-old had brought two oil paintings, one of the King and another of the Princess of Wales, her husband and their children.

Mr Mar said: ‘The royal family are like an anchor for uncertain times – especially when you see the mess of politicians.’

He added: ‘They are the only steady political institution amid the turmoil in the United Kingdom and, really, what is the only steady institution for the future of this country?

‘It’s still royalty. They’re harmless. They’re not politicians. Whether you’re right, left, middle, whatever it is, you look up to them.’

The artist said his painting of Kate, which invoked Biblical imagery comparing her to Mary, was intended to poke fun at the ‘religious fervour’ he thought surrounded the birth of her most recent child, Prince Louis, in 2018.

Also today, royal commentator Richard Fitzwilliams told MailOnline: ‘Kate’s appearance today is pivotal as the royal family is much weakened by two senior members fighting cancer. It is especially significant as we have not seen her on an official engagement since December.

‘It is clear, both from the moving video message in March and from the statement released yesterday, that she is resilient.

‘The new photograph emphasises this aspect of her character too, but she is also having an extremely tough time, as those undergoing chemotherapy usually do.

‘The details we were given of her condition are an attempt to help other sufferers from this pernicious disease.

‘There will be considerable speculation as to what events she will be able to attend during the summer. They will have a very special cachet as today’s Birthday Parade will. She is a very special person with a place in all our hearts.’

Last night, Kate issued a candid statement outlining her personal cancer journey and said she is experiencing ‘good days and bad days’ as she undergoes chemotherapy.

But she has begun to work from home, undertaking meetings with her foundation and Kensington Palace team, and hopes ‘to join a few public engagements over the summer’ but stressed ‘I am not out of the woods yet’.