It is constitutional convention in the United Kingdom that the royal prerogatives are only carried out on the advice of the responsible minister. It is clear that it would be a political and constitutional outrage for the Queen to act without advice or to refuse to act when advised.
I want to know how this process works technically. I read that if the government wants to carry out a royal prerogative, an order-in-council is required which involves meeting with the Queen in person.
Does the Queen just needs to express consent verbally or does she need to actually sign anything? Are there witnesses present? Can the document be signed (if it has to) on behalf of the Queen by another person?
After that, how does it continue? Does the Prime minister just walk out of the meeting and claims that the Queen has agreed and then orders somebody to carry out the prerogative? (e.g. in case of prorogation of parliament: does he just tell it to the Speaker, Black rod, etc. himself?) Or is there another chain of command that involves the Queen mandatory, i.e. she herself has to give the order to somebody?