Contesting a Will: Undue Influence and Testamentary Capacity UK

Updated: 16 May 2026 • Reading time: 9 min

Not every will that reaches probate is a valid expression of the deceased’s true wishes. Where a will was made under pressure, by someone who lacked mental capacity, or in circumstances that raise doubt about its authenticity, it can be challenged in court. Understanding the legal grounds — and the high bar required — is essential whether you are considering a challenge or trying to protect a will you have made.

The Main Grounds for Contesting a Will

1. Lack of Testamentary Capacity

The foundational test for testamentary capacity comes from Banks v Goodfellow (1870). The testator must, at the time of executing the will:

• Understand the nature and effect of making a will
• Understand the extent of the property they are disposing of
• Understand the claims of those who might reasonably expect to benefit
• Not be suffering from any disorder of the mind that distorts their judgment in these respects

Critically, capacity is assessed at the moment the will was signed — not at death. A testator with dementia may still have had capacity on a “lucid day.” Medical records, witness evidence, and the solicitor’s file are all used to reconstruct the testator’s mental state at the relevant time.

Where the testator had capacity when giving instructions but may have lacked it by the time of execution, the rule in Parker v Felgate (1883) may save the will: if the testator understood they were signing a will prepared from instructions they gave when capable, that may suffice.

2. Undue Influence

Undue influence in probate law is a high bar. Unlike contract law (where presumed undue influence can arise from certain relationships), in wills the claimant must prove actual coercion. The test from Hall v Hall (1868) requires that the influencer’s pressure “bows the will without convincing the mind” — the testator must be shown to have acted against their own wishes, not merely to have been persuaded.

Conduct that is not enough to establish undue influence:

• Persuasion, however persistent
• Emotional pressure or appeals to affection
• Caring for the testator and thereby gaining influence over them
• Repeatedly raising the topic of the will

What can establish undue influence:

• Threats — physical, financial, or emotional
• Isolation of the testator from family and friends
• Evidence that the testator expressed a different intention when the alleged influencer was absent
• The beneficiary controlling all communications with the solicitor

Undue influence claims are difficult and expensive. Direct evidence is rarely available — the coercion necessarily happens in private. Courts scrutinise the circumstances carefully but will not infer undue influence merely from a surprising outcome.

3. Want of Knowledge and Approval

Even if a testator had capacity, a will is invalid if they did not know and approve its contents. This ground arises where:

• The will was prepared by someone who benefits from it (a suspicious circumstance)
• The testator was blind, illiterate, or unable to read the will themselves
• There is evidence the contents were misrepresented to the testator

Where suspicious circumstances exist, the burden shifts to the propounder of the will to prove the testator knew and approved its contents. Evidence from the solicitor about how instructions were taken, and how the will was read to or by the testator, becomes decisive.

4. Fraud or Forgery

A forged will — one where the testator’s signature was not genuinely made or witnessed in the manner required — is void. Fraud includes cases where a third party misrepresented facts to the testator to procure a gift. Forensic handwriting evidence and document examination are typically required.

5. Failure of Formalities

Under section 9 of the Wills Act 1837, a will must be in writing, signed by the testator (or by another person in their presence and at their direction), and witnessed by two or more independent witnesses who are present at the time and who each sign the will. A will that fails these requirements is void — though courts have limited discretion to admit an otherwise defective document.

The Golden Rule for Solicitors

In Kenward v Adams [1975], Templeman J established the “golden rule”: when a solicitor is asked to prepare a will for an elderly or seriously ill person, they should arrange for the testator’s capacity to be assessed by a medical practitioner, and that assessment should be recorded and kept with the will file.

This is not a legal requirement — a will made without such an assessment is not automatically invalid — but compliance with the golden rule provides strong evidence of capacity in any later challenge. Its absence can make a will more vulnerable.

Protecting Your Own Will

• Use a solicitor and insist on being seen alone for at least part of the consultation
• If you are elderly or unwell, ask for a capacity assessment and have it placed on the solicitor’s file
• Write a letter of wishes explaining your reasons for the distribution
• Keep the will with a reputable will storage service or probate solicitor
• Review and re-execute the will if your circumstances change significantly

Frequently Asked Questions