This is Money - Can someone with dementia make a valid will? Lawyers explain how to do this sensitively, and avoid future inheritance disputes

SFE director Holly Chantler and SFE member Katie de Swarte appear in This is Money and Hannah Herbert, technical counsel at the STEP trade body for inheritance professionals, says: 'It is possible for someone with dementia to make a will.
'The level of understanding required to prove they have the requisite capacity will vary from case to case, for example depending on the complexity of the estate.'

https://www.thisismoney.co.uk/money/pensions/article-11628617/Can-dementia-make-valid-will.html