Prince Charles’s subjects will today discover whether they will be permitted to know what he has been writing to government ministers.
The highest court in the land is due to rule on whether the “black spider letters” – so-called because of the Prince’s distinctive scrawl – should be made public so people can scrutinise the work of those in power, or remain confidential to preserve the heir to the throne’s privacy.
The Supreme Court ruling is likely to end a 10-year legal battle that began in 2005 when the Guardian journalist Rob Evans asked to see 27 letters exchanged between Prince Charles and Blair government ministers between September 2004 and April 2005.
In 2012 an independent tribunal of three judges ruled the journalist could see the letters.
But Dominic Grieve, the Attorney General at the time, used his ministerial veto to keep the letters private, on the grounds that they were written as part of the Prince’s “preparation for becoming king”.
Any perception that Charles had disagreed with the government of the day, Mr Grieve argued, "would be seriously damaging to his role as future monarch because, if he forfeits his position of political neutrality as heir to the throne, he cannot easily recover it when he is king".
The case went to the Appeal Court, which found in favour of the newspaper – at which point a Guardian spokesperson said: "The public has a right to know if the heir to the throne is advocating policy or promoting causes to government ministers. We hope the Attorney General will recognise he has reached the end of the legal road.”
Instead the Attorney General’s department took the case to the Supreme Court in a two-day hearing last November.
While the letters have – until now – remained private, the case has already revealed insights into the Prince’s dealings with ministers.
One 2010 hearing was told that Charles has been writing to ministers since at least 1969, when the 21-year-old Prince gave Prime Minister Harold Wilson the benefit of his views on the plight of Atlantic salmon.
At the same hearing, Paul Richards, a former adviser to Hazel Blears, the ex-Communities Secretary, claimed that when one black spider letter arrived, “it was treated with great reverence and went straight to the top of the pile in the red box containing the minister's business for the day, over and above letters from other ministers and even cabinet papers".
Mr Richards also claimed that Charles had written to Yvette Cooper about the design of eco-towns, and complained to Ed Balls, then education secretary, over changes to the primary school syllabus.
Some of the Prince’s earlier letters have also been leaked, most notably a 2002 missive to Tony Blair in which he told the then Prime Minister, at the height of the debate over the fox hunting ban, that he agreed with farmers who believed they were victimised more than "blacks or gays".
The leak prompted St James’s Palace to take the unusual step of issuing a statement defending the Prince’s letter writing, saying: “The Prince of Wales… believes part of his role must be to highlight views in danger of not being heard.
“This role can only be fulfilled properly if complete confidentiality is maintained. It is not about exerting undue pressure or campaigning privately."