When a Will is challenged: What recent high court case teaches us about mental capacity and unfounded delusions 

Making a Will is often seen as a straightforward step in planning for the future. Most people assume that once a document has been signed and witnessed, their wishes will be respected after their death. However, a recent High Court decision confirms that things are not always so simple. In some circumstances, a Will can be declared invalid for a number of reasons, including if the person making it did not have the necessary mental capacity at the time or was made on the basis of unfounded delusions or false beliefs. 

The case of Ginger v Mickleburgh [2026] EWHC 100 (Ch) is a recent example of how disputes over capacity can arise and how carefully the courts will examine the circumstances surrounding the making of a Will.  

The background to the dispute 

The case concerned the estate of Michael Gwilliam, who died in 2022. Several years earlier, in 2014, he had made a Will that significantly changed how his estate would be distributed. Prior to the 2014 Will, Mr Gwilliam would have died intestate (without a will) which would have meant his four daughters would have inherited his Estate in equal shares. Instead, the Will largely benefited his sister, nephews and an ex-girlfriend, leaving his daughters only a 25% share of his assets.  

After his death, the daughters challenged the validity of the Will in the High Court. Their argument was that their father did not have the mental capacity required to make a valid Will at the time it was signed as he had been suffering from unfounded delusions. They said he was suffering from late-onset schizophrenia and had developed fixed and irrational beliefs that they were conspiring against him, trying to have him sectioned for their own gain and trying to take his money. They said that these unfounded delusions directly influenced his choices. 

The case involved a large amount of evidence, including witness testimony, medical records and expert psychiatric opinion. Somewhat surprisingly, the Court gave little weight to the evidence of the experienced solicitor who prepared the Will. The Court found that, despite knowing Mr Gwilliam had been sectioned, a formal medical assessment was not obtained with the solicitor relying on casual comments from a nurse. In addition, an unauthorised third party stayed in the room whilst the Will was prepared which clouded the credibility of instructions. Further, the solicitor failed to keep a detailed attendance note or record of the meeting which, in the view of the Court, meant it was harder to prove it happened correctly. 

Ultimately, the court concluded that Mr Gwilliam had been suffering from delusions which directly influenced his decision to change his Will and therefore lacked the requisite testamentary capacity to make the Will validly 

Because those delusions affected the way he distributed his estate, the judge found that he lacked the necessary testamentary capacity at the time the Will was made. As a result, the 2014 Will was declared invalid.  

What does “testamentary capacity” actually mean? 

Under English law, a person must have what is known as testamentary capacity in order to make a valid Will. In simple terms, this means they must understand what they are doing and the effect of their decisions. 

The courts generally expect that the person making a Will understands the nature of the document, the extent of their property, and who might reasonably expect to benefit from their estate. Importantly, any mental illness or delusion must not distort those decisions.  

This does not mean that someone with a mental health condition cannot make a Will. What matters is whether the condition actually affects their ability to make rational decisions about their estate. It is also important that any solicitor instructed to prepare such a will, takes detailed careful notes and considers the need for a capacity report. 

Lessons for anyone making a Will 

Cases like this highlight some important practical points for anyone thinking about their own Will. 

First, capacity matters at the time instructions are given for the making of a Will. Even if someone appears generally capable, a Will can be challenged if evidence later shows that mental illness, dementia or delusions affected their decision-making at the time. 

Second, unusual or unexpected decisions can raise questions. Leaving out close family members is not unlawful, but it may increase the risk of disputes if the reasoning behind the decision is unclear or appears linked to mistaken beliefs. 

Third, proper professional advice is crucial. Solicitors experienced in Will-writing are trained to assess whether a client appears to have capacity. Where there are concerns, they may recommend medical evidence or capacity assessments to protect the validity of the Will. 

Finally, the case highlights how emotionally difficult these disputes can become. In Ginger v Mickleburgh, the litigation lasted several years and involved extensive evidence and court proceedings before the issue was resolved. 

A reminder of the importance of getting it right 

For most families, making a Will is about providing clarity and avoiding conflict after death. But as this case demonstrates, problems can arise if there are questions about mental capacity or the circumstances in which the document was prepared. 

Taking professional advice, documenting decisions carefully and addressing potential concerns early can all help ensure that a Will reflects genuine intentions and stands up if it is ever challenged.