A legal challenge to a decision which blocks the disclosure of letters the Prince of Wales wrote to ministers will be heard at the High Court today.
The case, brought by the Guardian newspaper, follows the announcement last October by Attorney General Dominic Grieve that he was imposing a veto on the release of correspondence between Charles and seven Government departments.
The Lord Chief Justice Lord Judge, sitting with Lord Justice Davis and Mr Justice Globe, will hear the judicial review action over the veto by Guardian News and Media at a hearing in London.
Grieve, the Government's principal legal adviser, said his decision was based on his view that the correspondence was undertaken as part of the Prince's "preparation for becoming king".
Making the letters public could potentially damage the principle of the heir to the throne being politically neutral, and so undermine his ability to fulfil his duties when king, he said.
The Government had been ordered to disclose letters sent by Charles during a seven-month period in 2004 and 2005 after a journalist won a freedom of information appeal.
Three judges at a freedom of information tribunal ruled in favour of Rob Evans, of the Guardian, who had challenged a decision by the Information Commissioner to uphold a refusal by the Government departments to release the correspondence.
The judges ruled that Evans was entitled to "advocacy correspondence'' written by Charles – described as letters he had written seeking to advance the work of charities or to promote views.
But Grieve issued a certificate under the Freedom of Information Act vetoing disclosure of the correspondence.
In a written statement last year the Attorney General said: ''I consider that such correspondence enables the Prince of Wales better to understand the business of government; strengthens his relations with ministers; and enables him to make points which he would have a right – and indeed a duty – to make as monarch.''
He added: ''If such correspondence is to take place at all, it must be under conditions of confidentiality. Without such confidentiality, both the Prince of Wales and ministers will feel seriously inhibited from exchanging views candidly and frankly, and this would damage the Prince of Wales' preparation for kingship.''
The seven Government departments to which the Prince wrote are Business, Innovation and Skills; Health; Children, Schools and Families; Environment, Food and Rural Affairs; Culture, Media and Sport; the Northern Ireland Office and the Cabinet Office.
Making his announcement last year Grieve said his decision to "exercise the veto in this case was not taken lightly".
He said he had taken into account the views of the Cabinet, former ministers and the Information Commissioner "in considering both the balance of the public interest in disclosure and non-disclosure and whether this is an exceptional case".
Grieve said: "My view is that the public interest favours non-disclosure. I have also concluded that this constitutes an exceptional case and that the exercise of the veto is warranted."