Catherine, Princess of Wales, will not be returning to royal duties with an appearance at the Colonel’s Review, a military parade in London in early June, as she continues her treatment for cancer.

The ceremonial display on June 8 is the traditional dress rehearsal for the King’s official birthday parade known as Trooping the Colour, which takes place a week later on June 15.

It is not yet clear if Kate will also miss that annual military spectacle – a highlight of the royal calendar full of pomp and pageantry – at Horse Guards Parade in the British capital.

It had been widely hoped that the popular 42-year-old royal might oversee proceedings at the run-through in her capacity as Colonel of the Irish Guards. The regiment will be trooping its colour – presenting its regimental flags – at this year’s ceremony.

Lt. Gen. James Bucknall will step in to take the salute in Kate’s absence. The former Commander of the Allied Rapid Reaction Corps has been to every Sovereign’s Birthday Parade since 2009 when he was appointed Colonel of the Coldstream Guards, having served as a Coldstream Guards Officer for more than 45 years.

The Princess of Wales has not carried out any public engagements since December and had been expected to return to official duties after Easter. However, in March, she revealed her cancer diagnosis and that she had started chemotherapy.

Following the announcement, a royal source told CNN that she would not be returning to frontline royal duties until she has been cleared to do so by her medical team.

There had also been speculation over whether King Charles would participate in next month’s Trooping the Colour as he continues his own cancer treatment. However, Buckingham Palace has now confirmed his attendance.

In a slight change from last year, the 75-year-old monarch will inspect troops from a carriage rather than on horseback. He will conduct the review in an Ascot Landau carriage seated alongside his wife, Queen Camilla.

The adjustment reflects previous guidance from the royal household that each engagement involving the King would be reviewed, with adaptations made based on doctors’ recommendations.

Charles announced his own cancer battle in February but recently resumed public-facing royal engagements as he continues his treatment.

The Trooping the Colour celebration usually sees members of the royal family gather on the balcony of Buckingham Palace to wave to crowds after the parade.