A good solicitor will ask for one if they have any doubts on this issue.
My uncle was sectioned for a month with severe depression. He made his will a year later when he was completely recovered, but the solicitor asked about his mental health and then asked for a certificate from a doctor or psychiatrist. It meant had there been any questions asked later, they had the evidence that he was in sound mind when the will was made.
Lending/gifting money to children


