Thanks for the link to that website. I hadn't understood what Nearest Relative meant before and that it wasn't just a broadening of the concept of next of kin to include non-traditional family relationships. I now understand that it refers specifically to a lay person with strong links to the patient (often a caregiver relative) to be consulted on behalf of that patient when they are mentally impaired or mentally ill.
This link defines who can be NR:
http://www.rethink.org/carers-famil.../nearest-relative-rights-information/what-who