What is the legal test for a solicitor to execute a will for an elderly woman with dementia?

Such circumstances pose a challenge for solicitors. The caselaw suggests that at the least a solicitor must make a serious attempt to determine whether the testator had capacity, and where there is possible doubt or reason to suspect a challenge a memorandum or note of the solicitor’s and conclusions should be retained in the file. This observation of Collity J. in Scott v. Cousins appears to seek a balance: ...Some of the authorities go further and state that the solicitor should not allow a will to be executed unless, after diligent questioning, testing or probing he or she is satisfied that the testator has testamentary capacity. This, I think, may be a counsel of perfection and impose too heavy a responsibility. In my experience, careful solicitors who are in doubt on the question of capacity, will not play God - or even judge - and will supervise the execution of the will while taking, and retaining, comprehensive notes of their observations on the question. The profession has also been warned on numerous occasions that the fact that an elderly person suffers from a form of dementia, and has lost capacity, may not be immediately apparent to those who are not closely associated with her. ...