A Supreme Court ruling that a couple’s intended heir should not be disinherited by a mix-up in the signing of mirror wills could lead to a flood of litigation, probate experts said this week.

They were commenting following the judgment in Marley v Rawlings and another, in which Lord Neuberger, president of the Supreme Court, said that the wills of Maureen and Alfred Rawlings should be treated in the same way as a commercial contract in that an obvious oversight should not be allowed to invalidate the testators’ wishes.

Richard Roberts, chair of the Law Society’s wills and equity committee, said the case could lead to more practioners bringing cases to court under the concept of clerical error. ‘There is a danger that some practitioners might start waving the flag,’ he said.

Lesley King, professor at the University of Law, agreed that the ruling could lead to more litigation. At the moment the law states clearly that a will has to be signed to be valid, she said. ‘This is taking a much more flexible approach, and as soon as there is a more flexible approach there is more opportunity to push the boundaries.’

James Lister, associate at top-50 firm Charles Russell, said: ‘The risk of a “floodgates” scenario for those seeking to continue to widen the notion of “clerical error” is clear, and we are likely to see more claims being brought in relation to seeking to uphold or amend wills which would not have previously been possible before today.’

Matthew Duncan, head of private client practice at London firm Kingsley Napley, said while the concept of clerical error has now been given a wider meaning by the Supreme Court, any resulting litigation would depend on the facts of each case.

The case concerned mirror wills which Maureen and Alfred Rawlings drafted in 1999 intending to leave their entire estate to Terry Michael Marley, who was not a blood relation. However, due to an alleged oversight by a solicitor, the two accidentally signed each other’s will.

The mistake came to light after Alfred Rawlings’ death, when his two sons argued that their father’s will was invalid because it had been signed by the wrong person. In 2012 the Court of Appeal upheld a High Court decision that it had no power to change the will and thus Alfred Rawlings had died intestate.

In the Supreme Court judgment Lord Neuberger said: ‘Whether the document in question is a commercial contract or a will, the aim is to identify the intention of the party or parties to the document by interpreting the words used in their documentary, factual and commercial context.’

The appellant was represented by Robert Ham QC and Teresa Rosen Peacocke, who were instructed by London firm Hugh Cartwright & Amin. The respondents were represented by Nicholas Le Poidevin QC and Alexander Learmonth, instructed by London firm Gillan & Co.