Understanding mental capacity

Parties contesting a Will typically claim there was undue influence on the person making it, or that the testator lacked mental capacity at the time. Inheritance disputes reaching the High Court have risen sharply over the past decade, with many more settled in the county courts - and in some cases the legal costs consume a large portion of the inheritance.

How capacity is assessed

The common-law test comes from Banks v Goodfellow (1870). John Banks had spent years in an asylum and suffered delusions, yet the court found he was still capable of deciding who should benefit from his estate. The test asks whether the person: understands the nature of making a Will and its effects; understands the extent of what they are giving away; can comprehend and appreciate the claims to which they ought to give effect; and has no disorder of the mind that perverts their sense of right in disposing of their property.

Why process protects you

Capacity disputes are not rare curiosities - reported cases such as Clitheroe v Bond [2021] show challenges consuming years and a substantial share of the estate. A professional involved in the Will-writing process should not act for anyone they suspect lacks capacity - and their assessment, made and recorded at the time, is powerful evidence if the Will is later challenged. If there are any doubts, a capacity assessment should be requested and carried out by a suitably qualified individual, with the report retained on file alongside the testator's instructions. At Kinherit, capacity is considered across a course of in-depth conversations, all calls are recorded, and the record sits alongside the Will itself. If a court ever asks what the position was on the day, the answer exists.

Capacity and Lasting Powers of Attorney (LPAs): plan while you can

Capacity is also the gateway to a Lasting Power of Attorney: you can only make one while you still have it. Lose capacity first and the door closes - your family's only route is a Court of Protection deputyship, which typically takes six months to a year, costs thousands rather than the modest LPA registration fee, carries ongoing annual supervision, and puts the choice of who acts for you in the court's hands rather than yours. If you want control over who can make decisions for you when you can't, the LPA conversation cannot wait.

Reform on the horizon

The Law Commission's 2025 report on modernising Wills law recommended that the Banks v Goodfellow principles be incorporated into the Mental Capacity Act 2005 Code of Practice, bringing the capacity test under one statutory framework. We welcome that direction - see our full analysis of the Law Commission recommendations. The Government gave an initial response welcoming the case for reform; its full response, and any Bill, are still awaited.

Key takeaways

• Capacity is judged at the time the Will was made - contemporaneous records are decisive
• Recorded, professional process makes a capacity challenge far harder to run
• Reform is coming: the capacity test may soon sit under a single statutory framework

Every Kinherit plan is built by a STEP-qualified estate planner, with recorded calls as standard.