These were introduced on 1st October 2007 and there are two parts:
They are totally separate documents from your Will.
If you are over 18 years of age then you should have a Lasting Power of Attorney Deed.
It is not age sensitive - you can be rendered incapacitated overnight because of a stroke or an accident.
Your spouse or close family member does not have a legal right to speak on your behalf without having a registered Lasting Power of Attorney Deed.
This means that they cannot pay your bills even though you have money in the bank or decide where you live or set up a care package to keep you in your own home.
If you did lose capacity those around you will face terrible turmoil which will be alleviated by you having had the forethought to address this issue whilst you still can.
It is too late once you cannot understand what you are signing.