Judges in the Court of Appeal have ruled following the break up of a civil partnership for the first time.
City high-flier Peter Lawrence was unhappy that a High Court judge had awarded his former partner £1.7m of their £4m in joint assets.
The 47-year-old equity analyst, who earns more than £390,000 a year, complained that his former partner, actor Don Gallagher, did not deserve that large a share.
Three judges in the Court of Appeal allowed his challenge after a hearing in London.
The couple split up after a civil partnership which had lasted seven months, although they had previously cohabited for over 11 years.
Mrs Justice Parker had decided, following a hearing in the family division of the High Court in June 2011, that Gallagher should get nearly £1.7m.
Gallagher's legal representative previously argued that it would be "inconceivable" that the family courts would approve the kind of settlement Mr Lawrence was seeking in the context of a heterosexual marriage of a similar duration.
But appeal judges disagreed and said the award to Gallagher should be reduced.
Gallagher, who is in his mid-50s, was an actor who had played a lead role in the stage version of Priscilla Queen of the Desert and Lawrence, who is in his late-40s, was an analyst at investment bank JP Morgan.
The two men began living together in 1997 at a flat in Clink Wharf, central London, and entered into a civil partnership in 2007, the appeal court heard.
Judges were told that the couple, whose joint assets also included a cottage in Amberley, West Sussex, separated in 2008.
Justice Parker had said Lawrence should get the London flat and Gallagher "Pine Cottage" in Amberley - which was his "pride and joy".
Judges were told that the London flat was worth "more than twice" the West Sussex cottage.
Lawrence's solicitor, Sarah Higgins, of law firm Charles Russell, said later: "Mr Lawrence is pleased that the order has been varied and that the matter has been concluded."
"The case was not in fact about the principles of civil partnership, which are the same as on divorce, but about how to divide assets which were largely brought into the relationship by one party.
"The particular issue in this case was how much Mr Gallagher should receive in relation to the increase in value of a property owned by Peter Lawrence which shot up in value simply as a result of London property prices."