The Princess of Wales has made a triumphant return to public life in the midst of her cancer treatment and joined the royal family to celebrate the King’s official birthday.

Kate and her three children, Prince George, Princess Charlotte and Prince Louis, were cheered by crowds in The Mall as they left 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 was in doubt after she missed the final Trooping rehearsal last weekend, but with the King also suffering from cancer the spectacle of military pomp and pageantry became a symbolic statement by the monarchy after a period of uncertainty.

She was surrounded by other members of the family, with her husband the Prince of Wales, Colonel of the Welsh Guards, on horseback, as were the Princess Royal, Colonel Blues and Royals, and the Duke of Edinburgh, Colonel Scots Guards.

The King also rode in a carriage with the Queen, a departure from last year because of his illness, and he will inspect the officers and guardsmen on Horse Guards Parade in Whitehall from the coach rather than from a horse.

Kate said in a statement on Friday she was making “good progress” with her treatment, but candidly said she has “good days and bad days” and although she has been working from home, said “I am not out of the woods yet”.

Support from the public has made a deep impression on the princess, who said she had been “blown away” by the “kind messages” that had made a “world of difference to William and me and has helped us both through some of the harder times”.

She 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.

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 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.

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.

When the inspection of the Guardsmen in their scarlet tunics and bearskins began, the King cast his eye over the servicemen who are fighting soldiers when not performing ceremonial duties.

Sat beside him in the carriage was the Queen who wore a pale green silk crepe dress and coat by Anna Valentine, Philip Treacy hat and her Grenadier Guards military brooch.

During the pageantry the colour was first trooped through the ranks of soldiers before the guardsmen marched past the King, first in slow then in quick time with the King acknowledging the command of “eyes right” with a salute.

For the first time in more than 100 years, soldiers on parade were allowed to have beards.

The rule change, which applies across the Army, was approved by the King earlier this year after facial hair was only allowed for religious, medical or role specific reasons.