A hotel porter has won £85,000 of his ex-wife's £500,000 National Lottery prize in the High Court because she had used some of it to buy a family home.
Judge Mr Justice Mostyn said the prize was "non-matrimonial property".
However, when the woman used some of it to buy a house she converted "part of her non-matrimonial assets into matrimonial property".
His decision is thought to be the first ruling on a lottery prize following divorce by a judge in England.
The judge announced his decision after a private hearing in the Family Division of the High Court in London. The couple's identities were not disclosed by order of the judge.
He said the porter had actually lived in the house for a "relatively short period" and was not entitled to "anything like" an equal share of its value.
Mr Justice Mostyn issued a written ruling which said: "In this case I [had] to consider the treatment to be awarded to a lottery prize of £500,000 in financial remedy proceedings following divorce."
He added that, while there have been "at least five reported decisions on the subject" in Australia, of a dispute over a lottery win, he had no knowledge of any similar decisions made in English courts.
The judge said the couple had separated several years ago, some three years after the wife had won the £500,000.
She used the cash to buy the London property which was worth £275,000, and now thought to be worth nearly £500,000.
Mr Justice Mostyn said where a husband or wife was "unilaterally buying tickets from his or her own income", without the knowledge of their partner, then it was easy to see the prize as a "receipt by that party alone" and therefore as non-matrimonial property. But she had made part of it into matrimonial property when she bought the house.