Princess Haya Bint al-Hussein, a wife of the ruler of Dubai, Sheikh Mohammed Al Maktoum, has left her husband - a highly unusual move for a senior royal in the UAE.
She has applied for a protection order in the High Court in London, and is seeking wardship of her children.
Sources told the BBC she was in fear for her life as she prepared for the court battle with her husband.
She is said to be hiding in a townhouse in central London.
She was conspicuously absent from Royal Ascot this year, despite being an Olympic rider and a regular at races.
Princess Haya was born in May 1974. Her father was King Hussein of Jordan, and her mother was Queen Alia al-Hussein. She was just three years old when her mother was killed in a helicopter crash in the south of the country.
The current ruler of Jordan, King Abdullah II, is her half-brother.
The princess spent a lot of time in the UK as a child. She was educated at two private schools, Badminton School in Bristol and Bryanston School in Dorset, before studying Politics, Philosophy and Economics (PPE) at Oxford University.
She has previously told interviewers that she has a passion for falconry, shooting and heavy machinery, and she claims to be the only woman licensed to drive heavy trucks in Jordan.
She took up horse riding as a young girl and found a passion for the sport, and in her 20s she pursued a career as a full-time professional equestrian athlete. The highlight of her riding career came when she represented Jordan in the 2000 Olympics in Sydney and was her country's flag bearer.
'I am lucky to be close to him'
On 10 April 2004, aged 30, Princess Haya married Sheikh Mohammed - the vice president and prime minister of the UAE, and the ruler of Dubai. He was 53 at the time, and Princess Haya was his sixth and "junior" wife. He reportedly has 23 children by his different wives.
Like her, he was keen on horses: he was the founder and owner of Godolphin horse-racing stables. The couple were wed in a ceremony in Amman. In the years since, Princess Haya has spoken effusively in public about her relationship with Sheikh Mohammed, painting a picture of perfect family life.
"Every day I am amazed by the things he does," she told Emirates Woman magazine in 2016. "Every single day I thank god that I am lucky enough to be close to him."
But cracks appeared to show last year when Sheikha Latifa, one of Sheikh Mohammed's daughters, tried to flee the country. In a video that spread worldwide, the 33-year-old princess claimed she and her family "did not have freedom of choice" in their lives, and that she had been subjected to abuse.
Sheikha Latifa reportedly escaped the UAE by sea with the help of a Frenchman, but was intercepted by armed men off the coast of India and returned to Dubai. In December, photos were released of her sitting next to the former Irish president Mary Robinson at home in the emirate.
The authorities in Dubai insisted Sheikha Latifa had been "vulnerable to exploitation" and was "now safe in Dubai". At the time, Princess Haya echoed the statement, saying it was "unimaginable that this thing has gone so far from the truth".
But now, just over six months later, sources close to Princess Haya told the BBC that she had discovered disturbing facts about Sheikha Latifa's attempt to flee and been subjected to increasing hostility and pressure from members of her husband's extended family. She reportedly no longer felt safe, and fled to Germany before moving on to the UK with her children.
She has now applied for a forced marriage protection order and a non-molestation order in the UK High Court in London - as well as wardship of her children.
Her husband has not responded formally to reports about their marriage. He did post on Instagram on 10 June, accusing an unidentified woman of "treachery and betrayal".
In court, he has asked for his children to be returned to Dubai.
Princess Haya is said to be living in an £85m ($107m) house in Kensington Palace Gardens.