John, it is probably a lasting Power of Attorney and there are two types Property and financial affairs and Health and Welfare, it is possible to complete both and they must be registered. The person with POA is required to act in the best interest of the donor (person who needs attorney), who must have had mental capacity when they register the POA.
If you have queries you can contact the office of the Public Guardian 0300 456 0300, you may also like to look at the Mental Capacity Act 2005.