The Prince of Wales is fighting a move that would force him to open up the Duchy of Cornwall, his 700-year-old private estate, to public scrutiny, arguing that it is not a public authority.
The dispute centres on how millions of oysters are farmed on the Helford River, near Falmouth, Cornwall, which is owned by the Duchy.
In 2011, an Information Rights Tribunal ruled that the Duchy was no longer exempt from freedom of information laws and must therefore disclose information on activity that impacts the environment under Environmental Information Regulations.
However, the Duchy, which last year provided the Prince with an income of nearly £20 million, lodged an appeal before successfully applying for a stay of proceedings while a test case concerning whether private bodies can be treated as “hybrids” of private and public bodies was heard in the European Court.