That's not strictly true. It's the Crown that is the font of all power. Parliament legislates as the Crown in Parliament - hence the mace must be present in th

That's not strictly true. It's the Crown that is the font of all power. Parliament legislates as the Crown in Parliament - hence the mace must be present in the chambers while Parliament is sitting and all bills must receive royal assent to become Acts of Parliament. There also exist powers that are (currently) outwith Parliament - namely the royal prerogatives. The court system is similar, courts derive their power from the Crown, although, of course, they are subject to statute passed by Parliament.