Three animal welfare charities are fighting to preserve almost £500,000 left to them by a woman who made no provisions for her daughter.
The case was heard at the Supreme Court on Monday.
The judgement will decide whether it is reasonable for parents to leave their wealth to charities if they fail to make adequate provision for their offspring.
Last year, the Court of Appeal ruled that Melita Jackson’s daughter – who was cut out of the will – should receive £164,000.
Heather Ilott had made the application under the Inheritance (Provision for Family and Dependants) Act 1975 for “reasonable financial provision” from her mother’s estate.
However, Blue Cross, the Royal Society for the Protection of Birds, and the Royal Society for the Prevention of Cruelty to Animals will now dispute the ruling, in order to “affirm the importance of testamentary freedom and secure crucial guidance for the future”.
In a statement, they said: “The charities have appealed this decision in order to obtain essential clarity from the Supreme Court regarding the scope of the court’s power to interfere with a person’s testamentary wishes using the 1975 Act.”
Melita Jackson’s inheritance has battled its way through the English courts since her death in 2004, aged 70.
She allegedly abandoned her daughter at age 17 after she left home to live with her boyfriend, who she later married.
No provision was made for the daughter – now a mother-of-five on state benefits – in her will, while her entire £486,000 estate was left to charity.
In 2007, a County Court awarded Ms Ilott £50,000 on the grounds that her mother had acted in an “unreasonable, capricious and harsh” way towards her. She later successfully challenged that award in the Court of Appeal.