The Privy Council and the Royal Charters: how does it all work? | Inforrm's Blog: "Privy Council is a body set up under the “Royal Prerogative”. It is not bound by any rules of procedure. Indeed, it appears that there are no rules, for example, as to its quorum (although this is conventionally treated as being three, with four members usually in attendance) along with the Queen.
The Privy Council is not a deliberative body. Its meetings are short and formal – lasting only for a few minutes with everyone remaining standing. Discussion or deliberation does not take place.
By convention, the “Queen in Council” always follows the advice of her ministers.
In other words, the Privy Council is, in substance (although not in form) a sub-committee of the Cabinet. It executes the orders of Ministers.
The best and most comprehensive recent treatment of the subject can be found in Patrick O’Connor QC’s 2009 JUSTICE paper (linked)" 'via Blog this'