The Prince of Wales' private estate is fighting a court ruling that could open up its dealings to increased public scrutiny.
Representatives for the Duchy of Cornwall are appealing against a decision that it is a "public authority" and must therefore hand over environmental data about a controversial oyster farm it owns.
In November 2011 the estate was ordered to hand information concerning the environmental impact of the Port Navas oyster farm in Cornwall to local campaigner Michael Bruton, who claims that the farm is causing damage to the natural habitat.
The farm, owned by the Duchy of Cornwall Oyster Farm Ltd, cultivates non-native Pacific oysters in the Lower Fal and Helford special area of conservation, near Falmouth.
The order was made after John Angel, principal judge of the First-Tier Tribunal on information rights, a court that deals with legal battles relating to freedom of information, overturned a ruling by the Information Commissioner in October 2010 that the Duchy was not a public body subject to the regulations.
He ruled that under the Environmental Information Regulations (EIR) 2004, the Duchy of Cornwall is a public authority.
However, Thomas de la Mare QC, representing the Duchy argued in an appeal that the estate does not have "legal personality".
He said: "Is it not a natural or legal personality. The Duchy is in fact shorthand for the land owned by the Duke, subject to restrictions contained in a charter.
"None of the relevant powers are the powers of the Duchy, as opposed to the Duke."
Adding that the estate did not exercise any public functions, he continued: "None of the relevant powers in question, save perhaps the ceremonial aspects, are concerned with service of public interest.
"There is no separate legal personality for the Duchy.
"Any claim that it does have such separate legal personality may present consequences outside this litigation."
The EIR are part of the freedom of information regime in the UK which implements a European directive requiring public authorities to disclose environmental information unless an exception applies.
Mr Bruton first submitted a request for information in September 2008, and it was refused by the Duchy on the basis that the EIR did not apply because it was not a public authority, the hearing at the Rolls Building in central London was told.
The Duchy of Cornwall maintains it is not a public authority under EIR and therefore does not have to deal with the request.
But in November 2011 the tribunal ruled that it was a public authority, a ruling which could open its private dealings up to increased public scrutiny.
The Duchy of Cornwall is the estate given to the heir to the throne, comprising of around 53,628 hectares of land in 23 counties, mostly in the south west of England and including the whole of the Isles of Scilly. It also has an extensive financial investment portfolio.
It was created in 1337 by Edward III for his son and heir, Prince Edward the Black Prince, who became the first Duke of Cornwall. Its website says its primary function is "to provide an income from its assets for the Prince of Wales".