The Prince of Wales's private estate has won an appeal against a ruling which could have opened up its dealings to increased public scrutiny.
Representatives for the Duchy of Cornwall successfully challenged a decision that it is a ''public authority'' and must disclose environmental data about a controversial oyster farm it owns.
In November 2011 the estate was ordered to hand over information said to concern 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.
But, in a ruling just released, an appeal tribunal declared that the estate "is not a public authority" under environmental information rules.
Mr Justice Charles, president of the Upper Tribunal (Administrative Appeals Chamber) ruled that "the Duke of Cornwall is under no obligation" to provide the information sought by Mr Bruton.
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 environmental information disclosure 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 is a public authority.
But the appeals tribunal disagreed and ruled in favour of the Duchy.
Mr Justice Charles said in his written ruling: "The information sought does not exist but no point has been taken that this appeal is academic.
"This is because the underlying legal issues are relevant to another request Mr Bruton has made, other requests that he and others would like to make, and more generally."
The appeals tribunal accepted arguments by lawyers for the Duchy that, for the purposes of the EIR and the Environmental Information Directive 2003/4, the estate does not have ''legal personality'' and does not exercise any public functions.
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 is the estate given to the heir to the throne, comprising 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''.