Prince Charles letters: minister's veto of publication was lawful, court told The Guardian has campaigned for nine years to see the "black spider memos." But what are they? Our multimedia team explain A senior government minister acted lawfully when he overrode a court and vetoed the publication of secret letters written by Prince Charles, the supreme court heard on Monday. James Eadie, QC for the government, rejected suggestions that the use of the veto by Dominic Grieve, who was attorney general at the time, was an "intrinsically suspect or objectionable constitutional aberration." He told the court that parliament had taken "a carefully considered, deliberate decision" to give ministers such as the attorney general power to override rulings by the freedom of information tribunal "to protect the public interest where real and significant issues arise." Grieve overruled three judges who had decided the public had the right to see how the prince had written to ministers in an effort to influence official policies.‬ Eadie was opening the government's latest attempt to keep a set of such letters secret. Backed by the prince, it has refused a freedom of information request from the Guardian for copies of the correspondence for nine years. Lord Neuberger, the president of the supreme court, and six leading judges will consider legal arguments for two days before delivering a judgment at a later date. The prince has gained a reputation for writing private letters to government ministers promoting his views. The letters have been called "black spider memos" because of his scrawled handwriting.‬ At issue in the supreme court hearing are 27 letters exchanged between the heir to the throne and ministers in seven Whitehall departments between September 2004 and April 2005.‬ Three judges in a freedom of information tribunal ruled in 2012 that the letters should be disclosed, on the basis that the public was entitled to know how and when the prince sought to influence government.‬ Grieve, however, used his power of veto to overrule the tribunal, arguing that publication would seriously damage Charles's future role as king. He said the letters had to be kept secret to preserve the prince's political neutrality.‬ The court of appeal ruled in March that Grieve's use of the veto had been unlawful. Lord Dyson, the leading civil judge in England and Wales, and two senior judges decided that Grieve had "no good reason for overriding the meticulous decision" of the tribunal.‬ On Monday, Eadie told the supreme court it was plain that parliament had given ministers the power to veto rulings from the tribunal on reasonable grounds when the freedom of information act was passed. "It is acknowledged that it is unusual for parliament to bestow on the executive a power to override a decision of a tribunal or court," he said. However there is nothing constitutionally out of the ordinary in parliament deciding that the ultimate primary decision-maker on where the public interest lies in the context of disclosure should be the executive. It is clear that parliament decided ... that the highest level of government should be permitted to have the final say as to whether information, the disclosure of which it considered to be damaging to the public interest, should be disclosed. He also said that "a premise that the veto is some form of intrinsically suspect or objectionable constitutional aberration" lay at the heart of the court of appeal's decision that Grieve's use of the veto had been unlawful. He added that the power of veto was based on the "premise that a democratically accountable senior minister is ultimately best placed to assess the public interest." Dinah Rose QC is due to put the Guardian's case on Tuesday.‬ Last week the newspaper revealed how Charles was set to reshape the sovereign's role by making "heartfelt interventions" in national life when he becomes king.‬