"Advance decision" means a decision made by a person ("P"), after he has reached 18 and when he has capacity to do so, that if—
at a later time and in such circumstances as he may specify, a specified treatment is proposed to be carried out or continued by a person providing health care for him, and
at that time he lacks capacity to consent to the carrying out or continuation of the treatment,
the specified treatment is not to be carried out or continued.
For the purposes of subsection (1)(a), a decision may be regarded as specifying a treatment or circumstances even though expressed in layman's terms.
P may withdraw or alter an advance decision at any time when he has capacity to do so.
A withdrawal (including a partial withdrawal) need not be in writing.
An alteration of an advance decision need not be in writing (unless section 25(5) applies in relation to the decision resulting from the alteration).