Kate Middleton has been out of the public eye for a number of months as she receives treatment for cancer.

The Princess of Wales has issued a personal apology to the Irish Guards as she missed the traditional rehearsal for Trooping the Colour.

Kate Middleton, who is currently receiving preventative chemotherapy as she recovers from cancer, didn’t attend the Colonel’s Review on June 8 as she would usually do in her role as Colonel of the Irish Guards.

While little has been heard of the Princess since she shared news of her illness in a deeply personal video back in March, a letter penned by the royal mother-of-three has now been released. In it, she wrote apologised to the Irish Guards for missing the event, writing she was ‘proud’ of the regiment and sending her ‘best wishes.’

She wrote, ‘I wanted to write and 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 this year has been practising for months and dedicating many hours to ensuring their uniforms and drill are immaculate.

‘Being your Colonel remains a great honour and I am very sorry that I’m unable to take the salute at this year’s Colonel’s Review. Please pass my apologies to the whole regiment, however, 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.’

In recent weeks, reports about the Princess of Wales have seemed positive, with sources suggesting she has been seen ‘out and about more’ after ‘turning a corner’ with her preventative chemotherapy.

Yet, Kensington Palace has also stressed the need for ‘space and time’ for Kate Middleton to recover, with sources suggesting last month that she won’t be returning to royal duty till the autumn at the earliest. ‘No one wants to put any pressure on Catherine,’ an insider told MailOnline last week. ‘The only thing that matters at the moment is her getting better. She has been through an ordeal this year.’

Despite Kate’s absence, The Trooping of the Colour Ceremony is still due to go ahead on 15 June. It celebrates the Sovereign’s official birthday and dates back to the seventeenth century. Last year’s event saw King Charles ride on horseback during the parade, marking the first time the reigning monarch has done so since 1986, when Queen Elizabeth II last rode. She later travelled in a carriage (as Queen Camilla and the Princess of Wales did at last year’s event). This year, King Charles will travel in a carriage with the Queen amidst his own cancer battle.

Insiders said last week the Princess is feeling ‘a lot better’ amidst her cancer treatment. Speaking to Vanity Fair‘s Katie Nicholl, they said, ‘It has been a great relief that she is tolerating the medication and is actually doing a lot better.’ Meanwhile they added that ‘everyone has rallied around’ the Princess, including the Prince of Wales and the Middletons, who have always been known to be a tight unit.

The new update will be a welcome relief to royal fans, with MailOnline stating last week the Princess has been seen ‘out and about more’ with her family.

Speaking to People magazine, an unnamed insider said, ‘William is prioritising giving her all the time she needs to get better and the support, particularly to the children.’ According to sources, the Prince is ‘staying positive’ for his family, and relying on the ‘nuclear family unit’ of Kate’s supportive family; Carole, Michael, Pippa and James. Insiders went on to say Prince William has also developed a close bond with his father, who is also undergoing his own battle with cancer.