EXCLUSIVE: Greek heiress Athina Onassis splits from her Brazilian horseman husband 'Doda' after he was caught cheating by her security team at the couple's Florida home

Athina Onassis’s Olympic medal winning husband threw his decade-long marriage away on a one-night stand with the sister of an international equestrian, Daily Mail Online has exclusively learned.

‘Doda’ Miranda was found in bed with the blonde at the $2 million home that the heiress bought in the horsey-heaven of Wellington, Florida just last year.

Now Miranda is desperately trying to worm his way back into the life of the heiress who inherited half of the $5 billion fortune of her shipping magnate grandfather — Jacqueline Kennedy’s second husband.

‘I am really in the midst of a storm,’ Miranda, 43, admitted to Brazilian magazine Epoca,  ‘But I will not give up on my love.

‘It won’t be easy but I will fight until the end.’

Daily Mail Online has learned that Miranda — real name Alvaro de Miranda Neto — was discovered in bed with the woman by his wife’s security team, causing a scandal that has rocked the show jumping world.

Now ... and then: Athina Onassis, 31, at  the Global Champions Tour show jumping tournament on May 22  in Madrid (left) without her wedding band or engagement ring after her security caught husband Alvaro de Miranda Neto, known as Doda,  with found cheating with another woman. She was wearing her rings just months before

In one of the most recent photos of the couple together, taken last July, the couple are holding hands. Now Doda is desperately trying to worm his way back into the life of the heiress who inherited half of the $5 billion fortune of her shipping magnate grandfather -  Jackie Kennedy’s second husband

‘Doda’ Miranda was found  with a blonde at the $2 million home that the heiress bought in the horsey-heaven of Wellington, Florida just last year

Inside the home where Doda was discovered with a well-connected member of the international show jumping circuit a source told Daily Mail Online exclusively. 

Doda begged his wife's security team not to say anything, but one of them went straight to Athina. She immediately packed her bags and went off to Europe

‘Athina’s security detail is paid by her not him. They busted him having sex with another woman in the couple's new house in Wellington,’ a well-connected member of the international show jumping circuit told Daily Mail Online exclusively.

‘He begged them not to say anything, but one of them went straight to Athina. She immediately packed her bags and went off to Europe.

‘This has been the buzz in Wellington for about a month,’ added the source.

‘It was apparently a one-night stand, there was nothing serious going on between them.’

Doda was a member of Brazil’s Olympic showjumping team that won bronze medals in both 1996 and 2000. Athina, 31, is an international equestrian herself and hopes to represent Greece in this summer’s Olympics in Rio de Janeiro, Brazil.

She competed in the latest leg of the Longines Global Champions Tour in Chantilly, France, last weekend — without her wedding band. The website Greek Reporter said she looked ‘sad and haggard.’

The next leg of the tour is in Cannes starting June 9.

Sources say the woman that Miranda cheated with follows her sibling around to international competitions. Other high-profile members of the tour include Bruce Springsteen’s daughter Jessica, and Georgina Bloomberg, daughter of New York City’s billionaire former mayor, Michael Bloomberg.

Athina is having a bad year on the Longines tour, so far winning a total of just 50 Euros — about $56 — in four outings, according to the tour’s website. Last year she won more than $11,000 and in 2014, her best year, her prize money totaled nearly $70,000.

Athina competed in the Longines Global Champions Tour of Chantilly on May 26.  She is an international equestrian and hopes to represent Greece in this summer’s Olympics in Rio

Doda was a member of Brazil’s Olympic show jumping team that won bronze medals in both 1996 and 2000

Christina Onassis, daughter of Greek shipping magnet Aristotle Onassis, is seen with  Athina, at Le Jardin d'Acclimation in Paris, France.  Athina's early  childhood had been the stuff of dreams. Her mother gave her her own flock of sheep, complete with a shepherd, when she learned the nursery rhyme Baa Baa Black Sheep. She also gave her a private zoo

Athina holds her father's arm as she poses with him and his wife Swedish model Gaby Landhage and their children. After Christina’s death, Athina went to live with Roussel and Landhage

Any money she wins competing pales into insignificance compared with her immense wealth. She inherited an estimated $2.7 billion on her 18th birthday, and at the time was reported as the richest teenage girl in the world.

But her fortune has been badly managed over the years, experts say, and she sold the jewel in the Onassis crown — Aristotle’s private Greek island, Skorpios — to Russian billionairess Ekaterina Rybolovleva in 2013 for an estimated $100 million.

Her early childhood had been the stuff of dreams. Her mother Christina Onassis gave her her own flock of sheep, complete with a shepherd, when she learned the nursery rhyme Baa Baa Black Sheep. She also gave her a private zoo.

But all the money in the world could not shield the Onassis family from tragedy. Athina was just 3-years-old when Christina was found dead in her bath tub in 1988 aged 37. She had died of a heart attack brought on by years of eating disorders.

A decade and a half earlier, Christina had lost her entire family in little more than two years. Her 24-year-old brother Alexander was killed in a plane crash in January, 1973, their mother, Athina, died of a drug overdose the following year, and Aristotle, who never recovered from his son and heir’s death, succumbed in March 1975, leaving former First Lady Jackie a widow for the second time.

Christina had four marriages, none of them lasting more than three years. Athina, whose father was her final husband, French pharmaceutical heir Thierry Roussel, was her only child.

Athina inherited an estimated $2.7 billion on her 18th birthday, and at the time was reported as the richest teenage girl in the world

Christina had four marriages, none of them lasting more than three years. Athina, whose father was her final husband, French pharmaceutical heir Thierry Roussel (above) was her only child. Athina now has no contact with her father

Five years after the assassination of John F Kennedy, Jackie Kennedy married Onassis in 1968

Onassis with his first wife Athina (Tina) and children, Alexander and Christina. Christina had lost her entire family in little more than two years. Her 24-year-old brother Alexander was killed in a plane crash in January, 1973, their mother, Athina, died of a drug overdose the following year, and Aristotle, who never recovered from his son and heir’s death, succumbed in March 1975, leaving former First Lady Jackie a widow for the second time

Roussel fathered a son with Swedish model Gaby Landhage while Christina was pregnant, and the couple split shortly after Athina was born. After Christina’s death, Athina went to live with Roussel and Landhage.

Athina now has no contact with her father and has even dropped his last name. He wasn’t among the 1,300 guests invited to her December 2005 marriage to Miranda in a specially constructed Roman Catholic church at a posh resort in Sao Paulo, Brazil. Miranda’s father Ricardo led her down the aisle.

Athina finally seemed to have found happiness with her horses and her 12-years-older husband. She learned to speak fluent Portuguese and settled down to a comfortable new life in Brazil. They lived in a 17.000 sq. ft. apartment with 15 dedicated parking spaces.

But before they married, in February 24, 2003, shortly after arriving in São Paulo, she checked herself into a clinic, reportedly to have liposuction done on her abdomen and derrière at Doda's urging.

Doda told a Brazilian magazine they spent most of their time training, and only occasionally let their hair down. ‘We do have fun,’ he said. ‘But in a more low-profile way.

‘We go out every now and then, but we prefer a dinner to a discotheque.’

Athina played down her Greek heritage to such an extent that the Aristotle Onassis Foundation refused to have her on its board, calling her ‘someone who has no connection with our culture, our religion, our language or our shared experience, and who never went to college or worked a day in her life.’ She didn’t even visit the country that she now wants to represent at the Olympics, for 12 years.

Doda told a Brazilian magazine in 2011 that they intended to start a family within a few years. Athina reportedly became pregnant in 2013, but suffered a miscarriage

Athina competed in the latest leg of the Longines Global Champions Tour in Chantilly, France, last weekend — without her wedding band. The website Greek Reporter said she looked ‘sad and haggard'

Athina paid $12 million for a  20-stall barn, paddock and all-weather ring, complete with grooms’ accommodation, set on more than 5 acres of land in Wellington near her home

‘She can do whatever she wants with what she inherited from her mother, but not with Onassis’s legacy to the Greek people,’ said Onassis Foundation president Stelios Papadimitriou.

Miranda told a Brazilian magazine in 2011 that they intended to start a family within a few years.

‘Athina is still very young,’ he said, adding that having a baby would interrupt her budding showjumping career.

‘I also have a very busy life,’ he said. ‘When a baby comes I want to reduce the number of competitions to be more present.’

He said that Athina spent much of her time looking after Vivienne, his daughter with model Cibele Dorsa. Dorsa committed suicide in 2011 by jumping from a Sao Paulo apartment block.

Athina reportedly became pregnant in 2013, but suffered a miscarriage.

She and Miranda have lived primarily in Sao Paulo but they have another base in Europe. She bought the four-bedroom, five-bath property close to the Palm Beach Polo and Country Club in Wellington to be close to the center of the United States equestrian world.

She also paid $12 million for a nearby 20-stall barn, paddock and all-weather ring, complete with grooms’ accommodation, set on more than 5 acres of land.

There was no-one at Athina’s Wellington home when Daily Mail Online knocked. Many residents in much of the tony equestrian area of Wellington, a suburb of West Palm Beach, leave town when the circuit moves to foreign countries for the summer.

Three miles away, at Grand Prix Village, her $12 million barn was shuttered and the gates were padlocked.

Neither Athina nor Doda responded to requests for comment from Daily Mail Online.