King Charles is 'greatly shocked and saddened' after a soldier was thrown from their horse and died just moments after performing in front of him at the Royal Windsor Horse Show.
The individual, who was in the King's Troop, Royal Horse Artillery, is understood to have been fatally injured following an incident on Friday evening, Thames Valley Police said.
They are said to have fallen from their horse at around 7pm, having just exited the arena following the performance.
The military rider was given immediate treatment, but sustained serious injuries and died at the scene.
Police said next of kin had been informed and are being supported. The death is being treated as unexplained but non-suspicious.
The Royal Windsor Horse Show is continuing as planned, with the omission of The King's Troop, Royal Horse Artillery display.
Thames Valley Police chief superintendent Michael Loebenberg said: 'We are appealing for anyone with information or material relating to the sad death of a military rider at Royal Windsor Horse Show yesterday to please get in touch.
'Our thoughts are with the soldier's family and the wider community in the military and at the Royal Windsor Horse Show at this extremely difficult time.
'At this stage, we have not found any suspicious circumstances. We are working with the Ministry of Defence, the Defence Accident Investigation Branch and Royal Windsor Horse Show organisers HPower to gather as much information as possible to understand how this happened.'
A soldier in the King's Troop, Royal Horse Artillery, died just moments after performing in front of King Charles at the Royal Windsor Horse Show on Friday
King Charles III was seen watching the troop perform at the Windsor show on Friday
An army spokesperson said: 'It is with deep regret that we announce a member of The King's Troop Royal Horse Artillery died on Friday 15 May, following a tragic incident at the Royal Windsor Horse Show.
'The family has been notified, and our thoughts are with them at this sad and difficult time.'
Jo Peck, HPower Event Director, said: 'Our thoughts and sympathies are with the family of the soldier who sadly died yesterday.
'The Royal Windsor Horse Show will continue today as per the published timetable, with the omission of The King's Troop, Royal Horse Artillery display.'
Anyone with information is asked to call 101, quoting reference number 521.
The incident occurred just hours after the King and the Duchess of Edinburgh were pictured at the royal horse show on Friday.
Organisers said the Royal Windsor Horse Show would continue, with the omission of the troop. Pictured: King Charles arriving at the Royal Windsor Horse Show on Saturday
Charles went on a royal walkabout and greeted members of the public at the Royal Windsor Horse Show
Sophie was also seen alongside her daughter, Lady Louise Windsor, in a rare appearance from the young royal.
King Charles' niece, 22, has been present at the event, but also working away behind the scenes at her part-time job.
According to Nick Brooks-Ward, director of the event, the down-to-earth royal is operating a 'first concierge service'.
He told Vanity Fair: 'Lady Louise is one of the chief organizers, essentially operating a first concierge service.
'She's a great worker and a real asset to the team with no airs or graces. It's a proper paid job and there's no special treatment because of who she is.'
In addition to helping out behind-the-scenes, Lady Louise will also compete in the carriage driving event on Sunday.
The royal was taught to carriage drive as a young girl by her grandfather, the late Prince Philip, and the pair are said to have bonded over a shared love of the sport.
Lady Louise now frequently partakes in equestrian competitions and has driven her beloved grandfather's ponies as a way to keep his memory alive.
The monarch was seen shaking hands with young riders from the Pony Club on Saturday
King Charles took time to speak to the youngsters after arriving for the show's third day
She will participate in the Meet of the British Driving Society on Sunday, with Edward and Sophie expected to attend in their role as president and vice-president of the show.
Princess Anne and Prince Edward have also been in attendance at the event since it opene on Thursday.
Sophie, 61, who serves as vice president of the annual show, was spotted taking in the atmosphere on Friday
The Duchess of Edinburgh and her daughter Lady Louise Windsor pictured on Friday
The Royal Windsor Horse Show is a popular event among royals, and was said to be the late Queen Elizabeth II's favourite event on the royal calendar.
It first took place in May 1943 under the name the Windsor Horse and Dog Show.
The Royal Windsor Horse Show is the only time of year the private grounds of Windsor Castle are open to the public.