One morning, in the last year of her life, my mother – in the later stages of dementia – offered to make me a cup of tea. She turned the kettle on and then described what she was doing. “There are four stages to making a mug of tea,” she told me. “I talk myself through them so that I remember: tea bag in cup, hot water, milk, then sugar.” Her delight at being able to do this small thing for me was evident – she could still play “hostess”, make herself a brew first thing in the morning and...