Thanks, RP. So basically, in the event of The Queen being incapacitated to carry out her State functions, the Duke of Edinburgh, or if not living, their eldest child would be empowered to act as a kind of Power of Attorney (to put it in commoner terms)?
No, Prince Charles would become Regent, provided Parliament agreed The Sovereign was unable to carryout her duties of State due to health. A Regency can only occur with an Act passed by Parliament.
The Prince Regent would be empowered to carryout the duties and responsibilities of State set forth in the Act, including but not limited to, assenting to legislation, dissolving Parliament, calling up the military, having the right to be consulted, granting honours and creating new Peers.