One of the conditions which must be satisfied for a will to be valid is that the person making it must be of sound mind. With an ageing population, cases involving disputes over a testator’s mental capacity are becoming more common – it is estimated that up to two million people in the UK suffer from some form of dementia or brain injury.
Guidance on the meaning of mental capacity can be found on the Mental Health Foundation website.
The bar for a successful challenge to a will on the gorund of a lack of mental capacity is set high. Cases from 2013 onwards make it clear that recurrent mental illness (schizophrenia) and being 'grief stricken' do not necessarily mean that a testator lacks the mental capacity to make a valid will.