When someone becomes incapable of looking after their own affairs, the Court of Protection has power to appoint people (usually close relatives) to look after them. Such people are called Deputies.
Any major decisions concerning the patient have to be taken by the Court of Protection and we can act on behalf of the Deputies in making the necessary applications and dealing with the Court of Protection generally.
If possible, a Lasting Power of Attorney, made while someone is mentally capable, is preferable because this will remain valid even after the person granting it comes mentally incapable.