Christian Schmederer, who is in his forties and lives in Kensington, west London, took the action after Eva Kohn, 27, ended their relationship. In legal papers he claimed that she had duped him into believing she had thrown the ring away as part of a money-making scheme.
Yesterday the couple reached a settlement after Mr Schmederer launched the action to recoup the £90,000 he spent on the ring and £200,000 he gave her in cash.
Mr Schmederer, a City worker who earns £1m a year, claimed Ms Kohn had told a series of lies about her wealthy family from the moment the pair met.
He alleged that she pleaded for money after claiming that her mother had died and that her father had cut off her monthly allowance. It emerged that her mother, Carol, 52, was alive in Christchurch, Dorset, although Ms Kohn's father died several years ago. In his writ Mr Schmederer said he would not have proposed to Ms Kohn had he known the truth about her life.
He claimed that Ms Kohn said that it was her first engagement, although she had already been married, to Michael Suzuki Sagi, in a ceremony in October 2000 when she was 22.
Mr Schmederer, who works in the German and Austrian division of the banking giant JP Morgan, said he first gave Ms Kohn £100,000 on 3 March this year, and handed over another £50,000 two weeks later. In May, after they were engaged, he claims he paid a further £50,000 into her bank account.
But around a month later she ended the relationship and told him that she had thrown the diamond solitaire into the river. Mr Schmederer said the case was "distressing" but the couple had now reached a settlement. Ms Kohn, who is living in a £750,000 mews house in Chelsea, said: "I don't want to hurt anyone's feelings by discussing what was or wasn't said."
Papers filed by Mr Schmederer to the High Court last month state: "The claimant does not believe it was indeed the engagement ring that was thrown into the river, but if it was (and/or the defendant maintains it was so disposed of) the claimant claims damages equivalent to the cost of the same (ie, £90,000)."
The alleged episode over the ring has echoes of the reported spat between the England football star Wayne Rooney and his fiancée. The footballer hit the headlines after admitting to sleeping with a prostitute. The affair placed his engagement in jeopardy, with Colleen McLoughlin allegedly throwing her engagement ring into a squirrel enclosure. Treasure hunters were warned to stay away from the colony of red squirrels after it was reported that they were hiding the £50,000 ring.Reuse content