A judge has awarded a woman a £100,000 share of her former partner's home even though the couple were not married and she made no financial contribution to the mortgage.
The ruling could benefit thousands of other unmarried couples who under the current law have no special rights to each other's property when a relationship breaks down.
Elayne Oxley, 51, shared a home in Kent with Allan Hiscock, 54, for 16 years before she claimed a share of the property when he ended the relationship.
In a complex 50-page judgment Lord Justice Chadwick ruled that Ms Oxley is entitled to a 40 per cent share of Mr Hiscock's £232,000 home in Hartley, near Dartford.
Ms Oxley told the court that although she had not paid the mortgage she had contributed towards food and utility bills. She hailed the ruling a victory for unmarried women.
"Women who live with their partners assume they are protected but the law doesn't recognise the term 'common-law wife'. My case will prevent other women enduring the anguish I have been put through," she said.
Family law experts were more cautious. Nigel Shepherd, a spokesman for the Family Solicitors Law Association, said: "The case does not alter the fact that you do not get an entitlement to a property owned by your partner simply by virtue of living with them. There is still no such thing as a common-law marriage."
But he added: "Although not a landmark decision as such, the judgment clarifies the approach to be taken in this type of case and represents a more generous and fairer interpretation of what remains an extremely complex area of law."
Ms Oxley was working with social services when she met Mr Hiscock, an engineer at Dartford power station. "I wanted to be married to him but he didn't want to for tax reasons," she said.
Mr Shepherd said the case showed that there was a real need for a change in the law reflecting the rights of unmarried couples who lived together.