Natasha Livingstone: The 173 days Princess Kate was away left a huge hole in the UK’s heart

Wearing Princess Diana’s earrings and an Alexander McQueen royal blue coat, Kate’s megawatt smile, as she held her children’s hands and greeted Sandringham crowds on Christmas Day, betrayed not a hint that anything was wrong.

Bolstered by the joyful success of her star-studded carol service days earlier at Westminster Abbey, she looked set to have a bumper year ahead, with talk of a glamorous trip to Italy.

But as the whole world now knows, that patina of good health and happiness was illusory.

Kate’s attendance at St Mary Magdalene Church in Norfolk was to be her last formal public appearance for six months.

Her absence – a very long 173 days until Saturday’s Trooping the Colour – has left a massive hole in the heart of the Commonwealth.

As ever, it’s often only when we miss someone that we truly realise how much we treasure them.

After December 25, there was not a whisper from the Princess for 23 days. Perhaps that was not surprising. January is a quiet month in the royal calendar.

But then a heart-juddering announcement, out of the blue, on an icy Wednesday afternoon changed everything.

The Princess, Kensington Palace announced, had undergone “planned abdominal surgery” the previous day, January 16 – exactly a week after her 42nd birthday.

The procedure had been successful, and her condition was thought to be non-cancerous, but aides said she would remain in hospital for up to 14 days.

Ninety minutes later, Buckingham Palace announced more bombshell news: King Charles would be treated at the same London hospital for an enlarged prostate.

Suddenly, the core of the monarchy shifted from palaces to the polished wards of the London Clinic.

Royal engagements were replaced with bedside visits, ceremonial robes swapped for medical gowns.

After 12 nights, the King and the Princess were both discharged on January 29.

While Charles waved at well-wishers as he exited the front door with Camilla, Kate slipped out discreetly to be driven home to Windsor.

And so began her period of “recuperation”, with aides making it clear that her return to public duties would not be until after Easter and would depend on medical advice.

Amid this helter-skelter of royal health concerns, Buckingham Palace made another dramatic announcement on February 5: Charles had been diagnosed with cancer.

Suddenly the slimmed-down monarchy was looking rather threadbare, thrusting William – among others – further into the spotlight.

Throughout February, the Prince juggled caring for his wife and three young children with his royal duties.

Unbeknown to the public, it was towards the end of this month that Kate started a course of “preventative chemotherapy”, with “post-operative tests” having detected cancer.

She remained out of the public eye.

While the British media respected her privacy, a photo was published by the US gossip website TMZ on March 4.

It showed the Princess wearing sunglasses in the passenger seat of an Audi driven by her mother, Carole Middleton, near Windsor Castle.

Inevitably, ill-informed online gossip erupted, with the hashtag #whereiskatemiddleton trending.

As the unseemly chatter continued, the official message about Kate’s condition was muddied when, on March 5, the Ministry of Defence was forced to backtrack on claims that she would attend the practice parade for Trooping the Colour in June.

Readers will need little reminding of what happened on Mother’s Day the following Sunday.

In an apparent effort to reassure the public and squash vile internet rumours, the Palace released a photo of Kate beaming with Prince George, Princess Charlotte and Prince Louis.

It was said to have been taken by William a few days earlier at their home in Windsor.

Within minutes of it being made public, several seeming anomalies were spotted. Why were the hands blurred? Wasn’t there something strange about a jacket zip?

The Associated Press news agency issued a “kill notice”, saying the image had been manipulated – a decision followed by three other leading agencies.

In response, an unprecedented mea culpa was shared on Kensington Palace’s social media platforms.

Kate apologised for confusion, saying: “Like many amateur photographers, I do occasionally experiment with editing.”

The same afternoon, the Princess was photographed leaving Windsor in a car with William, who was looking at his phone while she turned towards the window.

Sources later revealed that she had been left “shell-shocked” at the furore surrounding the Mother’s Day photo and found the episode deeply upsetting.

Nobly, as his wife continued medical treatment, William ploughed on with official engagements alone.

Grim proof of how, for the royals, whatever the situation, the show must go on.

On March 18, a video was published by TMZ and The Sun newspaper showing Kate and William leaving the Windsor farm shop two days earlier.

Although a royal source said the fact that she looked “happy and relaxed” should squash the wild online conspiracy theories about her health, the video only fanned the flames.

Matters were made worse the following day when it was revealed that the London Clinic had launched an investigation into claims Kate’s confidential medical records were breached by at least one member of staff caught trying to peek at her notes.

Four days later, on March 22, the Princess broke her silence.

In a deeply emotional and brave video, Kate spoke of her “huge shock” at being diagnosed with cancer that was discovered in post-operative tests after her abdominal surgery.

Sitting alone on a bench in Windsor, her voice cracking, she spoke movingly about her condition, adding that she and William had done all they could to “process and manage this privately” for the sake of their three young children.

There were universal messages of goodwill and cancer experts praised Kate, saying that her words would help other families fighting the disease.

Palace sources explained that the Princess would continue with her private routine, with William set to return to official engagements after their children went back to school on April 17.

The Easter deadline, originally earmarked as the time the Princess might be able to return to work after her operation, came and went, as the Waleses spent the Easter weekend at their Anmer Hall home in Norfolk.

On April 18, William returned to public duties, chatting easily with volunteers at a food distribution charity in Surrey.

But his emotions were clear when he was given two cards wishing his wife and father well.

Five days later, Kate was appointed to The Order of the Companions of Honour – a unique honour for a member of the Royal Family, bestowed by the King, in recognition of her public service.

The same day, another family photo was released – this time without a hitch – to celebrate Prince Louis’s sixth birthday: an adorable picture of the lad taken by Kate.

William continued his engagements – telling staff during a school visit that his wife “would have loved” to join him.

But as the days grew longer, key dates in the royal calendar came closer and closer.

The nation yearned for some good news about Kate.

In a huge boost for the family, and the country, King Charles returned to work on April 30.

But not even his May 20 visit with Camilla to the Chelsea Flower Show – usually attended by the Royal Family en masse – could distract global attention from the Princess’s long absence from public life.

Now, though, it is so very apt that this absence should end with her attending the Trooping the Colour, an event at the heart of the nation’s history, displaying the British Army’s regimental flags (Colours) which traditionally provided a rallying point on the battlefield.

Kate has endured her own battles and everyone is praying for her to come through victorious.