Make No Mistake: Recognising Where Errors Can Arise In Wills

Drafting errors in wills and other legal deeds are inevitable because we’re only human. Law firms can buy in the most sophisticated of modern technology but this cannot guarantee against mistakes.

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If an error comes back to haunt us, we can so easily recognise with hindsight what should have been obvious at the time. Even so, it’s tempting to hear of other lawyers’ mistakes and take the view that, of course, we’d never make such a stupid error. The reality is, any private client lawyer is at risk of making an error – whether it’s a clerical error or a significant mistake.

The consequences are potentially significant (one of many reasons for professional indemnity insurance). And where it leads to a dispute and a resolution cannot be reached – the court may have to determine the proper construction of the will. We look at two recent cases where the courts had to decide on issues relating to mistake in the context of a will.

‘Mistake’ in a will

In Naidoo v Barto [2023] EWHC 500, the mutual will of a surviving spouse was declared invalid on the basis of undue influence exerted by one of the sons (David Barton). Barton is serving a lengthy prison term for defrauding wealthy care home residents at the family-run business.

Under his parents’ mutual wills, Barton was the sole executor and sole beneficiary - even though he had several siblings. On his mother’s death, another of her sons brought a claim on the grounds of undue influence.

He also argued that his parents’ mutual wills agreement was vitiated by a common mistake – the ‘mistaken belief’ being that entering into such agreement would leave the surviving spouse (Mrs Naidoo, in the event) free to make a new will if she changed her mind about leaving her estate to Barton.

The court rejected the claim on the basis of common mistake but accepted the claim of undue influence.

In his ruling, Cadwallader HHJ reiterated the fundamental principle that common mistake cases are those in which both parties make the same mistake of fact or law relating to the subject matter or the facts surrounding the formation of the contract. He added:

“One or both parties must have entered the contract under a positive belief which was incorrect, rather than merely not having thought about a particular issue. For a contract to be avoided for common mistake, there has to be a common assumption as to the existence of a state of affairs, no warranty by either party that that state of affairs existed, and the nonexistence of the state of affairs must not be attributable to the fault of either party; where it is possible to perform the letter of the contract, but alleged that there was a common mistake in relation to a fundamental assumption which rendered performance of the essence of the obligation impossible, the court must construe the contract in the light of all material circumstances in order to determine whether the contract should be avoided for common mistake (Great Peace Shipping Ltd and Tsavliris Salvage (International) Ltd [2002] EWCA Civ 1407)”.

He did not find a common mistake on the part of Mr and Mrs Naidoo at the time of their agreement. On the evidence, Mrs Naidoo knew the effect of the mutual wills agreement and that the survivor would be permanently bound to it. They should not, therefore, be rescinded on the ground of common mistake. They were, instead, set aside on the basis of undue influence.


In Mundil-Williams v Williams [2021] EWHC 586, the drafting of the will had been done negligently and the will was declared invalid because of the error made.

The dispute involved the will of John Williams - and a farmhouse. In short, he went to a Newport solicitors’ firm where a secretary took handwritten notes of his instructions and typed a detailed file note. During the meeting, she also completed a standard form containing the relevant information.

A paralegal who was tasked with drafting the will needed some issues clarified and she spoke further with Mr Williams by telephone. However, the instructions recorded by the secretary differed significantly from the instructions subsequently given to the paralegal as far as the farm was concerned.

After his death, one of his sons claimed the will was invalid for want of knowledge and approval. The court concluded that there was a critical mistake in the will: the farm had been included in a specific clause when it should have fallen into the residue. The mistake meant the will had not reflected Mr Williams’ true intentions.

The court listed several reasons for its conclusion, and it’s worth particularly picking out its observations that the paralegal had not gone through the initial instructions with Mr Williams in their phone call; and there was obvious room for confusion as to his intentions regarding the farm.

The court made an order excluding some wording from the will and admitting the amended version to probate.

Key takeaway

These two cases offer valuable lessons for practitioners:

  • To prove a claim based on common mistake, the appropriate test must be satisfied before a will can be rescinded. A simple misunderstanding or failing to think things through properly will not suffice. Where being able to prove on balance the existence of a common mistake existed could be a challenge – are there alternative grounds for challenging the will?
  • Care must be taken to ensure the final will properly reflects the testator’s intended wishes. Where more than one individual is involved in taking instructions, extra caution should be taken. In this case, it’s unclear whether an experienced solicitor reviewed the final will before it was executed. Given the circumstances – that in itself is telling.


Posted on 09.06.23