The Princess Royal has "sustained minor injuries and concussion" after an incident at her Gloucestershire home, Gatcombe Park, on Sunday evening, Buckingham Palace has confirmed.
In a statement, the palace has said that Princess Anne, 73 "remains in Southmead Hospital, Bristol, as a precautionary measure for observation and is expected to make a full and swift recovery".
It added: "The King has been kept closely informed and joins the whole Royal Family in sending his fondest love and well-wishes to The Princess for a speedy recovery."
HELLO! understands that Anne was out walking within her estate when the incident occurred, resulting in the Princess Royal sustaining minor wounds to the head.
While the exact cause of her injuries has not been confirmed, it's understood that her medical team say that her head injuries are consistent with a potential impact from a horse's head or legs.
Emergency services were sent to Anne's home and after medical care at the scene, Anne was transferred to Southmead Hospital in Bristol for appropriate tests, treatment and observation.
It's understood that Anne's husband, Vice Admiral Sir Tim Laurence, and her children, Peter Phillips and Zara Tindall were on the estate at the time of the incident. Sir Tim accompanied his wife as she was taken to hospital.
While the Princess has suffered concussion and minor injuries to the head, she is expected to make a full and swift recovery. No further details have been given about her treatment.
A palace spokesperson says Her Royal Highness is "recovering well, is in a comfortable condition and is being kept in hospital as a precautionary measure for further observation".
Future engagements
The Princess Royal keeps a busy schedule of engagements but a palace spokesperson has said: "On doctors’ advice, Her Royal Highness’s engagements for the week ahead will be postponed. Her Royal Highness sends her apologies to any who may be inconvenienced or disappointed as a result."
She will be unable to attend the Japan State Banquet at Buckingham Palace on Tuesday evening and will no longer travel to Canada later this week for a planned visit.
Where is Princess Anne being treated?
The palace confirmed that the Princess is being treated at Southmead Hospital in Bristol, around 30 miles from her Gloucestershire home.
Southmead Hospital is part of the North Bristol NHS Trust and has a number of major specialities, including neuroscience.
The Institute of Neurosciences is based in the hospital's Brunel building and is a regional centre providing specialised services for a wide spectrum of neurological conditions.
Southmead Hospital is also home to the only adult major trauma centre (MTC) in the The Severn Major Trauma Network (SMTN). The centre works alongside six other units based across the South West.
Equestrian career
The Princess Royal is an accomplished and confident horsewoman, having been the first British to compete in the Olympics, when she rode the late Queen's horse, Goodwill, in the equestrian three-day event at the 1976 Montreal Olympic Games.
Anne also won a gold medal in 1971 and two silver medals in 1975 at the European Eventing Championships.
Her daughter Zara has followed in her mother's footsteps with her own equestrian career and won a silver medal as part of Team GB's eventing team at the London 2012 Olympics.
Anne also rides on horseback during the King's birthday parade, but appeared to have some difficulties with an unruly horse at Trooping the Colour earlier this month.
With her being an experienced and skilled horsewoman, Anne was able to keep her horse under control without drawing too much attention away from the rest of the parade...
A difficult year for the royal family
Princess Anne's accident is the latest health upset to the hit the royal family this year, with both the King and the Princess of Wales diagnosed with and undergoing treatment for cancer, and Sarah, Duchess of York, having skin cancer.
Her absence will be keenly felt. The Princess Royal is a key member of the King's slimmed-down monarchy, and has played an important role in support of Charles since his diagnosis.
The princess, often dubbed the hardest-working royal, is known for her no-nonsense approach and her commitment to royal duty. This commitment was evident in today's palace announcement, in which Anne sent "her apologies to any who may be inconvenienced or disappointed as a result [of her absence]."
Joe Little, Managing Editor of Majesty Magazine told HELLO!: "The year 2024 has been a challenging one for the King and the Princess of Wales, so the news of the Princess Royal's incident makes you wonder what will happen next to members of the House of Windsor.
"However, the Buckingham Palace statement suggests that Anne is likely to make a speedy recovery. On her part the usually indefatigable Princess will be frustrated at having to withdraw from the Japanese state visit starting tomorrow [Tuesday] and at having to postpone a trip to Canada that was scheduled to begin later this week."
Family first for King Charles
While Anne is forever duty bound, the King's comments show that this is a monarch putting his family first.
When his daughter-in-law Kate underwent major abdominal surgery and began preventative chemotherapy following a cancer diagnosis, it has been widely reported that Charles encouraged the Prince of Wales to reduce his schedule and temporarily step back from duties to support his wife and children.
So while Anne may be itching to jump down into her busy diary once she is deemed fit and well by her doctors, no doubt her big brother Charles will advise her to take it easy.