The Princess of Wales has written to the Irish guards to apologise for being unable to take the salute and wish them luck for a trooping the colour event. The colonel’s review parade rehearsal for trooping the colour was taking place in central London on Saturday. In a letter read to the regiment, of which she is colonel, Catherine wrote: “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. 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.” Catherine, who is undergoing chemotherapy following a cancer diagnosis, apologised for being unable to attend. She wrote: “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. Please pass on my apologies to the whole regiment, I do hope that I am able to represent you all once again very soon. Please send my very best wishes and good luck to all involved.” The letter ended with the Latin phrase “quis separabit”, meaning “who will separate [us]?”, a motto associated with the British army in Ireland. The Irish guards posted a video of the letter being read to the regiment on X, saying: “The Irish guards were deeply touched to receive a letter from our colonel, Her Royal Highness the Princess of Wales, this morning. We continue to wish Her Royal Highness well in her recovery and send her our very best wishes. Quis separabit.” The regiment gave a round of applause after the letter was read out. The colonel’s review takes place seven days before the trooping the colour parade, which has been held on the sovereign’s birthday for more than 260 years. Catherine will be represented at the colonel’s review by Gen James Bucknall, who will act as the chief inspecting officer of the day in her absence. It is unclear whether Catherine will attend trooping the colour. In May, sharing an update on his wife’s treatment for an undisclosed form of cancer while on a visit to the Isles of Scilly, the Prince of Wales said she was “doing well”. Catherine has said she was “enormously touched” by the public support after she announced she was being treated for cancer in March. She said the discovery of the disease had been a “huge shock”.