Judges stressed the importance of making wills yesterday after ruling in the case of two members of a family who spent a "great deal of money" from their inheritance fighting over their share of a £500,000 estate.
Martin Densham-Smith claimed he was entitled to a half share of the money left by his father's second wife.
But Jonathan Fry, the second wife's own son, claimed he should have the lot and Mr Densham-Smith should have nothing.
Three judges at the Court of Appeal upheld a ruling that Mr Densham-Smith's father Denny and Mr Fry's mother Laura had made an oral agreement for mutual wills and the two sons should share the money equally.
Lord Justice Mummery said: "Ideally, Denny and Laura should have gone to solicitors with instructions that led to the drafting and execution of wills recording a mutual wills agreement.
"Instead, an untidy situation has arisen, which has unfortunately aggravated existing ill-feeling within a family and has cost a great deal of money to sort out."
Mr Fry, 51, had appealed against a finding at Guildford County Court claiming it was not supported by the evidence. He claimed that his mother was not bound to leave half to Mr Densham-Smith when she died in 2005, 15 years after her husband.
None of three wills she made after her husband's death left anything to Mr Densham-Smith, 58, and her final will left almost everything to Mr Fry.
The main asset of the estate is a 400,000 house in Tilt Road, Cobham, Surrey, bought by Mr Fry's mother and her former husband, John Fry, in 1956.
When they divorced in 1985, the house was transferred into her sole name and it became the new matrimonial home after Mr Densham-Smith's father sold his house in Normandy, Surrey, when the couple married.
The county court judge had found that Mr Densham-Smith had a good relationship with the couple but Mr Fry disliked his father-in-law and the dislike was mutual.
He said that if there had been no mutual wills agreement it would have meant that everything left by Denny would go to Mr Fry, whom he barely knew and did not like, to the exclusion of his own son.
Paul Norris, representing Mr Fry, told the judges at a hearing in October that it was "mere speculation" for the county court judge to say that the terms of his will suggested an agreement that on the death of his survivor, there should be equal shares for the two sons. The judges dismissed Mr Fry's appeal.