The ex of a multimillionaire former AirBnB boss is fighting for a £5m divorce payout, after claims she signed a deal that left her "virtually destitute" whilst high on "enough Xanax to sedate a horse".

Top business executive Martin Reiter - who masterminded the international growth of AirBnB and was also a senior boss at Wayfair and Groupon - married interior designer and cultural history expert Caroline Bauer-Reiter, 41, in 2012, with the pair enjoying a high-flying international lifestyle before splitting in 2018.

The pair separately moved to London from Berlin following the breakup, having signed an agreement in 2019 prior to their divorce which left the wife with no capital lump sum from her ex-husband's £17.3m fortune and no personal financial support after 2028.

Ms Bauer-Reiter went on to reopen the divorce fight in the Family Court in London, asking for more cash and claiming the "egregiously unfair" German agreement leaving her with no capital was "procured unconscionably," as before she signed it her then psychiatrist had given her enough Xanax tablets "to sedate a horse".

Her lawyers also argued that she is unable to work due to physical and mental health issues.

Family Court judge Mr Justice Cusworth ruled last October that the German order should be varied to hand her a divorce package made up of a £2.55m lump sum, plus £96,000 a year maintenance for the next 14 years and over £1m towards her legal costs, on top of five-figure annual child maintainance payments.

But the former couple are now fighting it out in the Court of Appeal, with the wife bidding to get her payout rolled up into a personal lump sum of around £5m.

The husband's lawyers meanwhile are seeking to overturn the "wholly excessive provision for the wife" ordered by the English judge and reinstate the German agreement, questioning her claims not to be able to work and insisting she has brought extra costs upon herself voluntarily by moving to London.

"The judge ought to have treated the wife like any other applicant for a variation who moves from say Macclesfield to Mayfair and seeks an increase in maintenance because she has chosen to live more expensively," the husband's barrister, Michael Horton KC, said.

The court heard that the former couple married in Austria in 2012 and lived in Berlin from 2016, but enjoyed a globetrotting lifestyle with their two daughters, now aged nine and 10.

They separated in 2018, with the financial separation deed being signed in Germany in 2019.

By that deed, they agreed that the wife would receive no capital lump sum, that the husband would pay her rent in Berlin until 2028 and give her personal maintenance of around £1,800 a month until August 2024, plus payments for the children.

In 2019, a divorce was granted by consent in Germany, with both parties stating that all financial matters had been previously agreed.

The husband then remarried in March 2023, moving to an £11.5m house in Holland Park, London, with his new wife.

Ms Bauer-Reiter then herself moved to London with the children only two months later in May 2023, having first obtained permission to do so from a German court.

She subsequently instructed top lawyers and went to the English divorce courts, seeking to revise the financial agreement she signed in Germany.

At the Family Court, Mr Justice Cusworth found the husband's net worth was £17.3m and ordered him to pay her the £2.55m lump sum, maintenance and over £1m towards her lawyers' bills.

Now before three top judges at the Court of Appeal, the husband's barrister, Mr Horton, argued that the "wholly excessive provision" should be overruled.

He said: "The judge considered that a substantial variation in terms of the maintenance provision was justified...he did so because of the wife's current and likely future inability to work and because the wife had moved to London and this had been judicially permitted."

Arguing against the wife's claim not to be able to work due to her health, the barrister said: "The husband's case was that the evidence...showed that the wife was living a perfectly normal life.

"The husband had seen evidence on the wife's social media, including an elaborate synchronised dance routine that contradicted her claims to poor health."

On the topic of more cash being awarded due to London being more expensive than Berlin, he likened it to a divorcing party choosing to move from a cheap to expensive area of the UK - such as Macclesfield to Mayfair - and demanding more money.

"This was a self-created increase in needs and the judge was wrong to allow this to justify an increase in the provision," he argued.

"The substance of the German deed was that the wife would meet her own needs from her own significant resources by a time not long after the children attained majority.

"The enormity of the difference between the provision in the German deed and the judge's order itself demonstrates that in reality this was no variation or modification but a decision where the judge has discarded the German deed completely and started from scratch.

"Just because there had been a change of circumstances, that did not give him free rein to consider the duration and quantum of provision as if starting from scratch.

"The husband submits that the scale of the increase from the German deed is excessive, coming six years post-separation and where the husband has remarried and has two more children.

"His position has since worsened even more. His net worth is now under £5m. He estimates that paying the interim order he has liquid funds to last only three months."

Rebecca Carew Pole KC, for the wife, however argued that the millions the wife had now been awarded is a "modest" sum and "unremarkable given the husband's overall wealth," pointing out that he lives in a "splendid" house in Holland Park, worth £11.5m.

"It is central to the wife's position...that the German notarised agreement was procured unconscionably and its terms were egregiously unfair to her," she said.

"The agreement...had been procured as a result of undue pressure, at a time when the wife was seriously psychiatrically unwell, vulnerable and heavily medicated."

She claimed that during the signing the wife was "very distressed...crying and had a panic attack" and that her then psychiatrist "had administered Xanax before the meeting and after she had a fresh distressed episode at the beginning of the meeting that she and (the psychiatrist) went outside the room and he forcibly administered her with two further Xanax pills in the toilet".

Xanax is a strong, fast-acting prescription tranquliser often used to combat anxiety issues.

"The agreement was vitiated as a result of the circumstances in which it was procured, which were unconscionable," she added.

The husband's barrister had also described the incident, saying: "The parties used the wife's treating psychiatrist...as a mediator...the deed was executed before the notary on 5 July 2019. The wife's oral evidence was that (the psychiatrist) had given her tablets 'enough to sedate a horse'."

Insisting that the wife cannot support herself, her barrister said she has Ehlers-Danlos syndrome, "a rare debilitating genetic condition that...disables her from working".

"The wife's condition deteriorated significantly as a result of her two pregnancies," she said.

"The wife's inability to work due to her EDS is at least in part a relationship-generated need, given the deleterious effect on her health of the pregnancies.

"The judge accepted the wife's evidence about her physical and psychiatric illnesses."

Ms Carew Pole went on to claim that whilst the husband says there has been "a dramatic collapse" in his fortunes, the reliability of his evidence is "seriously in doubt".

"In this case, the wife is suffering both hardship and a manifest injustice. The husband has been left with the entirety of the fruits of the marriage and the wife in penury.

"The English court is not prevented from making further provision. The wife was left virtually destitute following the parties' divorce in Germany."

She asked the court to not only uphold but reconfigure the payout awarded in the Family Court to give the wife a capitalised lump sum of around £5m.

The judges, Sir Andrew McFarlane, Lord Justice Moylan and Lord Justice Lewis, reserved their ruling on the case after a day-long hearing, to be given at a later date.