The High Court ruled today that Attorney General Dominic Grieve acted reasonably when he decided last year that the public had no right to see Charles' correspondence with seven UK government departments.
Grieve says the "particularly frank" letters reflect Charles' personal views and that Britons might not think that he is politically neutral as a monarch must be. The worry is that the institution would be undermined.
The Guardian newspaper has campaigned for eight years to have the documents released, claiming they would shed light on how the heir to the throne attempted to influence government ministers despite holding no elected position.