A man won a legal fight over a £70,000 inheritance today when the Supreme Court ruled that a will containing a "clerical error" should be rectified.
Terry Marley had lost challenges in the High Court and Court of Appeal.
But five justices in the Supreme Court ruled in his favour today after a hearing in London.
Judges heard that Mr Marley, now in his 50s, was taken in as a teenager by Alfred and Maureen Rawlings, and they treated him "as their son" even though they were not related.
They were told that Mr and Mrs Rawlings - who lived in Biggin Hill, Kent - had made wills in identical terms in 1999. Both agreed that Mr Marley should inherit after they had both died.
But each had mistakenly signed the other's will after an "oversight" by a solicitor.
Mrs Rawlings died in 2003 and the mistake came to light after Mr Rawlings died in 2006.
The couple's natural sons, Terry and Michael Rawlings, challenged the validity of their father's will.
They argued that the will was invalid and that their father had died intestate - therefore they should inherit.
A court fight had started and a judge had ruled against Mr Marley - saying Mr Rawlings' will did not comply with terms of the 1837 Wills Act and could not be rectified.
The Court of Appeal had agreed.
But the Supreme Court disagreed - after analysing evidence at a hearing in December.
One justice, Lord Neuberger - President of the Supreme Court - said the solicitor's "muddling" of the wills could legally be classified as a "clerical error" and the mistake could be rectified.
A legal expert said the Supreme Court had taken a "common-sense" approach and made an important decision.
"The Supreme Court has taken a common sense approach to interpreting wills in the same way commercial contracts have been treated for over 40 years," said Matthew Duncan, head of private client practice at law firm Kingsley Napley.
"The law has traditionally been generous in finding ways to fix errors in contracts. The Supreme Court saw no reason why the same principles should not apply to wills.
"Lord Neuberger was very clear that he would go as far as the letter of the law would allow in making sure Mr Rawlings' wishes were carried out."
He added: "Today's judgment is important because the concept of 'clerical error' has now been a given a wider meaning by the Supreme Court.
"To date, it was thought only typing errors could be fixed. This has now been extended to include mistakes arising from office work of a routine nature such as preparing, filing, sending, and organising the actual execution of a will."