Kate Middleton apologises for missing out on key rehearsal for Trooping The Colour - as she tells the Irish Guards 'I hope I am able to represent you all very soon'

Kate has apologised for missing out on a key rehearsal for Trooping The Colour.

The Princess of Wales has wrote a letter to the Irish Guards, who are presenting their colours to the King this year, saying: 'I hope I am able to represent you all very soon'.

Insiders have long emphasised that every cancer 'journey' is individual and believe speculation over whether Kate will attend key events such a trooping create unnecessary pressure at a time when she has asked for space and privacy.

It means the Princess of Wales will miss what would have been her first Colonel's Review, which had been due to take place today. 

The event is a dress rehearsal for Trooping and would have seen her take the salute as the new Colonel-in-Chief of the Irish Guards. 

The Colonel's Review comes before the King's official birthday celebrations on Saturday June 15, including their traditional Buckingham Palace ­balcony appearance. 

The Colonel's Review is identical to The King’s Birthday Parade, with the exception that some additional mounted officers ride on the latter.

Taking part will be over 1400 soldiers of the Household Division and The King’s Troop Royal Horse Artillery, including 400 musicians from the Massed Bands, all of whom will parade on Horse Guards for the second of two formal Reviews.

The Colonel's Review also includes 250 soldiers from the Foot Guards who will line the processional route along The Mall.

The Irish Guards have responded to the Princess's letter on Twitter, writing: '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.'

Meanwhile Buckingham Palace did confirm last week the Daily Mail's exclusive story in March that King Charles planned to attend Trooping and review the soldiers from a ­carriage, on doctor's advice, with Queen Camilla. 

He has previously taken part on horseback but it has been deemed prudent, given the length of the ceremony and the unpredictable weather, for him to be seated in an Ascot landau.

His Majesty is still undergoing treatment for his own unspecified ­cancer diagnosis.

He has now been given permission by his doctors to undertake more forward-facing public duties, although officials have stressed they need to carefully review each potential engagement, with adaptations made where necessary to prioritise his recovery.

While palace officials have been forced to cancel a number of public engagements in light of the General Election, key national and ceremonial events such as Trooping are not affected.

There was confusion in early March after the Ministry of Defence jumped the gun and published a statement on its ­website saying that the princess would be reviewing her troops, without seeking approval from Kensington Palace.

A few weeks after the MoD was forced to back down, the princess put out a moving video message in which she revealed that tests carried out after a successful abdominal operation revealed that cancer had been present.

Details of her cancer have not been disclosed but she has said that she was having 'preventative chemotherapy'.

Kensington Palace said it is confident the princess will make a full recovery.