A gay banker has won his appeal against a decision to award his former partner £1.7m of the couple's wealth.
Peter Lawrence, 47, claimed West End actor Don Gallagher was receiving more than he was entitled to because judges had taken into account a £2.4m London flat he bought before they got together.
The case is believed to be the first involving a civil partners to reach the Court of Appeal .
The men co-habited for 11 years but their civil partnership only lasted eight months and was dissolved in 2009.
A judge later awarded 54-year-old Mr Gallagher the couple's £900,000 Sussex cottage plus a payout of around £800,000 including some of Mr Lawrence's pension - around 45% of the couple's £4m estimated assets.
The court heard the actor - who appeared in musicals including Priscilla Queen of the Desert and Les Miserables as well as episodes of Casualty and Taggart - earned around £100,000.
Mr Lawrence, a high-flying analyst, had a salary of £390,000 from his job with City giant JP Morgan .
Judges heard how Mr Lawrence's flat, near fashionable Borough Market, had risen in value from £650,000 to £2.4m while the couple were together.
Mr Gallagher argued he was entitled to some of the value because he had played the major "home-making role", furnishing, maintaining and redecorating the property.
However, Mr Lawrence's lawyers said the fact he bought it before they became a couple meant it should be excluded from the calculations. They argued the couple had a "dual career" relationship.
A panel of three appeal court judges have now ruled in favour of Mr Lawrence and allowed his appeal.
Lord Justice Thorpe said same-sex partnerships enjoy exactly the same rights as straight marriages under the law but said the original financial calculations had followed "too theoretical a map".
The 55%-45% division of assets seemed unfair given the fact Mr Lawrence's flat had soared in value while the couple were together, he said.
"Whether approached on a needs basis or a fair-sharing basis, I would propose a lump sum of £350,000," said the judge.
The Law Commission is currently reviewing legislation on how married couples and civil partners can claim financial support from one another after a divorce or dissolution.
This includes looking at 'non-matrimonial' property which has been acquired before a relationship begins or has been received as a gift or through inheritance. The commission is expected to report back in 2013.
Divorce lawyer Ayesha Vardag commented: "The Court of Appeal's decision in Lawrence v Gallagher makes clear that the same principles for financial division apply to both marriages and civil partnerships.
"The reduction of Mr Gallagher's award was based on correcting the judge's application of the rules on matrimonial property, particularly on how to bring into account the family homes.
"It had nothing to do with any distinction between heterosexual and homosexual partnerships, and indeed makes clear that in this area of law no such distinction would be justified.
"As the court stated, 'The fact that the claim arises from the dissolution of a Civil Partnership rather than a marriage is of little moment.'
"The decision should reassure civil partners that they will be treated identically to married couples by the courts when they divorce."