http://www.legislation.gov.uk/id/asp/2000/4/enacted

PART 2CONTINUING POWERS OF ATTORNEY AND WELFARE POWERS OF ATTORNEY

18Power of attorney not granted in accordance with this Act

A power of attorney granted after the commencement of this Act which is not granted in accordance with section 15 or 16 shall have no effect during any period when the granter is incapable in relation to decisions about the matter to which the power of attorney relates.