The monarch isn’t above the law, it has been granted immunity from being sued but this is all entirely on the gift of parliament. Inside the robing room used just before she addresses the House of Lords is a copy of the death warrant for Charles I as a little reminder of who really is in charge.
The courts are literally the Queen’s. As for Charles I that was the result of losing a civil war and in case it’s not blindingly obvious exactly the kind of extralegal remedy I was referring to.
De jure but not de facto - It's the Crown Prosecution Service but it would be the stroke of a pen to change that, unless the Queen somehow mobilized the army any revolution would be swift and quiet.
