The King has stepped in for his absent daughter-in-law after her rare apology before one of the biggest events on the royal calendar.

On Monday (British time), the King presented new colours to Kate’s regiment, the Irish Guards, at Windsor Castle.

He inspected the guardsmen and officers on parade before the colours were blessed ahead of Saturday’s Trooping the Colour in London.

It follows the Princess of Wales writing to the Irish Guards at the weekend to apologise for not being able to take the salute and wish them luck for The Colonel’s Review in London.

Kate, who is colonel of the regiment, spoke of her pride in them and added that her position “remains an honour”.

“I wanted to write to you to let you know how proud I am of the entire regiment ahead of the Colonel’s Review and Trooping the Colour,” the letter – signed “Colonel Catherine” – said.

“I appreciate everyone trooping the colour this year has been practising for months, and dedicating many hours to ensuring their uniforms and drill are immaculate.

“Being your colonel remains an honour, and I am very sorry that I’m unable to take the salute at this year’s Colonel’s Review.”

The Colonel’s Review was held on Saturday. It is traditionally held a week ahead of the Trooping the Colour parade, which has marked the sovereign’s birthday for more than 260 years.

It remains unclear whether the princess, who continues her cancer treatment and recovery, will attend Trooping the Colour.

She has been absent from public duties since Christmas after first having major abdominal surgery. In March, she appealed for time, space and privacy for her family when she revealed she was being treated for an undisclosed form of cancer.

No firm date has yet been given for Kate’s return to public life.

Her letter was read out to the Irish Guards on Saturday.

“We continue to wish Her Royal Highness well in her recovery and send her our very best wishes,” the guards posted on X with footage.

The princess has a long history with the Irish Guards, even before she was named their honorary colonel in December 2022. She took over the role from her husband, Prince William.

She also missed the unit’s traditional St Patrick’s Day parade this year due to her ill health.

The latest update came as more details emerged about this coming weekend’s trooping the colour. It is understood the King will carry out the review of soldiers and officers from an Ascot Landau carriage with the Queen.

It is a change from last year’s ceremony, when he inspected the troops on horseback. That reflects Buckingham Palace briefings that the King’s engagements are being reviewed and adapted according to medical advice, as he continues his own cancer treatment.

The King and Queen are likely to travel by carriage in the traditional procession, and are expected to watch the trooping ceremony seated on a dais, rather than on horseback.

-with AAP