What might Prince Charles's letters reveal?
Seven Supreme Court justices are due to consider whether letters from Prince Charles to seven government departments should be made public.
This has been a lengthy and costly legal battle which should be nearing its end.
The focus on how Prince Charles operates has greater significance the closer he gets to the throne.
We know he'll be a different monarch to his mother, but just how different?
The Guardian newspaper and the prince's critics argue the public has a right to know what influence he exerts behind the scenes.
His supporters maintain he has a duty to contact ministers in private and his way of operating will change when he is king.
In the coming months, unless there's a referral on an issue of European law to the Court of Justice in Luxembourg, we'll have a resolution.
Either Prince Charles's confidential communications will remain just that.
Or his letters, which are often characterised by underlinings and exclamation marks, will be exposed to a wider audience than was originally intended.