The eldest child of the King of Thailand has died aged 47 in what could place a major question mark over Princess Anne's upcoming Asia tour.
Princess Bajrakitiyabha Mahidol, known in the southeast Asian nation as Princess Bha, had been in hospital for more than three years after suffering heart problems while out with her dogs.
The Thai royals had been quiet on her health since, though things took a turn for the worse just weeks ago.
In April, doctors found a stomach infection whih led to inflammation in her intestines, lowering her blood pressure to fall and leaving her with an irregular heartbeat.
Both her kidneys and lungs needed support through medical equipment, palace statements said.
There are now questions over who will succeed Thai King Maha Vajiralongkorn, who has seven children from four marriages.
Princess Bha was widely considered to be a well-suited heir to the throne.
She had been one of just three of the King's children to hold a royal title, alongside Princess Sirivannavari, 38, and Prince Dipangkorn, 20.
But the news comes just as Princess Anne was confirmed to be undertaking an official tour of South Korea and Thailand next month.
PICTURED: Princess Bajrakitiyabha arrives at a religious ceremony at The Grand Palace in Bangkok in 2020
|REUTERS
Mourners have been seen holding photographs of the King's eldest daughter after her death
|REUTERS
The Princess Royal will travel east with her husband, Sir Tim Laurence, from July 13 to July 17 - with questions likely to be raised over her schedule in Thailand.
In South Korea, the five-day visit carries particular significance as it will mark 75 years since the Battle of Imjin River, paying tribute to British servicemen who gave their lives during the Korean War.
Beyond the commemorative elements, the Princess Royal's programme aims to reinforce bilateral ties between Britain and both nations, encompassing diplomatic engagements, charitable work and cultural exchanges.
And in Thailand, the final two days of Anne's tour will see the Princess Royal hold an audience with the Thai Prime Minister as well as Their Majesties the King and Queen.
She will also pay respects to Her Late Majesty Queen Sirikit, the Queen Mother, during the visit.
READ MORE ON PRINCESS ANNE:
Princess Anne will visit Thailand in a matter of weeks
| PAThailand's Queen Mother died last October at 93.
Meetings with Thai female scientists and attendance at a regional health security showcase are also scheduled.
The tour will conclude with an event celebrating cultural collaboration between the UK and Thailand.
Princess Anne has previously visited the country in 1972, 1979 and 1987.
In Thailand, Princess Bha will be remembered for her prominent role in public life, her efforts to improve the livelihoods of female prisoners, and her diplomatic career.
PICTURED: Bands of friendship are tied around the wrists of the Queen, Prince Philip and Princess Anne in 1972 during their State Visit to Thailand
| GETTYShe studied law at Cornell University, obtaining a Master's degree and a Doctorate, and worked as an attorney in the Thai Office of the Attorney-General between 2006 and 2011.
From 2012 to 2014, she was Thailand's ambassador to Austria, Slovenia and Slovakia, before returning to the Attorney-General's office in Bangkok.
She also founded a charity promoting the rights of female inmates, particularly those who were pregnant while in jail.
In 2017, she was appointed as the goodwill ambassador for the rule of law in Southeast Asia by the UN Commission on Crime Prevention and Criminal Justice.
She transferred to the army in 2021, where she was bestowed the rank of a general and served as a chief of staff in the Royal Security Command.
The palace will now hold royal funeral rites, while the Government is expected to declare a period of national mourning.