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Mistake relating to documents

The general rule is that if parties sign a written document they are bound by it
(see L’Estrange v Graucob in Chapter 6). However, if a party has been induced
to sign under a misrepresentation or some unfair pressure, then the contract
will be voidable. In addition, two measures exist which may help where a
written contract is not in accordance with the parties’ original intentions

• the plea of non est factum,


• rectification.

Non est factum

In very limited circumstances the plea of non est factum may be available,
which literally means ‘not my deed’. It was proved successfully in the
following cases.

The second case is unusual, being recent, as the plea is not used a great deal
now. It is not allowed too easily, lest it be used as an excuse to escape an
unwanted contract, as was the fear in the following example.

Mistake 195

Foster v Mackinnon (1869)

An elderly man with poor eyesight was induced into signing a

document, being told that it was a guarantee. When it was found to be

a bill of exchange in favour of the plaintiff the court allowed the

defendant’s plea of non est factum.

Lloyds Bank v Waterhouse (1990)

A father who could not read or write signed an agreement as guarantor

for his son, thinking that it was for the purchase of a farm. In fact it was

also an agreement to be responsible for all of the son’s previous debts.

It was established that the father would not have signed the agreement

if he had known the true nature of it, and he had taken steps to ask the

bank for information. The plea of non est factum was upheld by the

Court of Appeal on this occasion.

Saunders v Anglia Building Society (1971)

(also known as Gallie v Lee)

Mrs Gallie, an elderly widow, was unsuccessful in her claim, as the

document which she signed was not very different from what she intended

to sign. Having broken her reading glasses, she was misled by her nephew

into signing a document which assigned the lease of her house to someone

else, whereas she thought she was giving it to her nephew as a gift.

However, the court did not think that what she had done was different

enough from her original intentions to amount to non est factum.