The King has presented a new flag to the mounted cavalry who will escort him to the first official birthday parade of his reign this weekend.
Charles was joined by the Princess Royal, who is the Royal Colonel of The Blues and Royals, for a special ceremony of prayers and blessings in the Buckingham Palace Quadrangle in which the flag was consecrated and officially became the new sovereign’s standard.
The King’s Cypher and Crown now appears on the new ceremonial standard which is made of silk damask, with gold thread embroidery and fringe.
It will be used for the first time in a public parade during Saturday’s Trooping the Colour in which The Blues and Royals will have a starring role.
Charles told representatives of the regiment that the standard represents a “personal bond between The Blues and Royals and the sovereign” which has lasted since before the Restoration in 1661.
He described it as “the golden thread which connects you to your illustrious past”, adding: “The battle honours displayed upon it, along with your uniforms and medals that are so visible in your ceremonial role, are a further demonstration of your proven track record as battle-hardened mounted and dismounted soldiers with recent operational experience.
“Indeed, I know that some of you are currently deployed on duty with the United Nations’ peacekeeping force in Cyprus.
“Such history pays homage to your dual role and that, of course, is the fundamental principle which makes state ceremonial and public duties so special and credible to a most grateful nation.
“In these difficult times for our country, as we continue to face an array of threats in many different forms, both domestically and internationally, it is all the more important to preserve such standards of excellence and achievement.”
There were 35 service personnel and 27 military working horses who were on parade for the event, which only takes place every decade.
The Blues and Royals were last presented with their standard by Queen Elizabeth II in May 2014.
A fanfare performed by four state trumpeters of the Band of the Household Cavalry in golden coats marked Charles’s arrival for Thursday’s ceremony.
He also received a royal salute from The Blues and Royals. Another salute was offered as the regiment paraded past Charles as they left Buckingham Palace at the end of the ceremony.
On Saturday, the regiment will provide a mounted sovereign’s escort for Charles from Buckingham Palace to Horse Guards Parade.
Major Peter Ireland, 47, of Thirsk, North Yorkshire, said it was an “incredibly special” moment for him to receive the standard from Charles on behalf of the regiment during Thursday’s event.
He said: “To receive this new standard from His Majesty, in the presence of our Colonel, The Princess Royal, and knowing that in two days’ time we will be carrying it in the sovereign’s escort in front of them both on the first King’s birthday parade for 70 years is incredibly special.”
Charles will be on horseback when he joins Saturday’s birthday parade, which will be the first time the reigning monarch has ridden at Trooping the Colour since 1986 when Queen Elizabeth II last rode.
Charles will take the salute as Colonel in Chief of the seven regiments of the Household Division during the event on Horse Guards Parade.
This year, the Welsh Guards’ Colour will be trooped at The King’s birthday parade.
Earlier on Thursday, Charles attended a thanksgiving service marking the 650th anniversary of the Anglo-Portuguese alliance, the oldest diplomatic alliance in the world still in force.
Portugal’s President Marcelo Rebelo de Sousa watched as readings and a psalm, both in English and Portuguese, along with music by composers of both nations were played during the celebration at The Queen’s Chapel in central London.
More than 300 activities and projects, involving 210 institutions, have been organised in both countries as part of the project.
The alliance, which is based on the perpetual friendship between the two countries, was first formalised with the signing of the Treaty of Tagilde on July 10 1372.
An original copy of the treaty, committing the nations to “peace, friendship and alliance”, was displayed at the chapel.
During the service, Maria Joao Rodrigues de Araujo, who has been the driving force behind the Portugal-UK 650 events, said the aim over recent years has been to “celebrate our shared history, writing new chapters of friendship and co-operation”.
She added: “We have undertaken scholarly research on the alliance and promoted the founding values enshrined in article one of the treaty of 1373: peace, friendship, truth, faithfulness, constancy, sincerity, kindness, and solidarity.”
Stating that more than 300 activities and projects had been organised in both countries and reached millions of people, she added: “We hope these long-term legacy projects and collaborations will help to cement the bonds of friendship between the citizens of both our nations, ensuring that the Anglo-Portuguese Alliance, the oldest alliance still in existence, continues to thrive.”
Foreign Secretary James Cleverly had earlier stated the relationship between the UK and Portugal “says something special about how we see the world and how our people get along”.
He added: “We are now building on those solid foundations to deliver security and prosperity for our countries, progress towards net zero, and support to Ukraine.”
