Prince Charles 'Black Spider Memos' Ruling Due

The UK's highest appeal court is set to rule whether the government acted unlawfully by preventing the release of Prince Charles' so-called "black spider memos".

The judgement from the Supreme Court is the latest step in a fierce 10-year legal battle to establish what the Prince has written to politicians about, and whether in the process he has overstepped the mark of political neutrality.

The notes have become known as the "black spider memos" because of the Prince's sprawling handwriting.

In 2005, Guardian journalist Rob Evans submitted a Freedom of Information request to find out how many letters Prince Charles had written to MPs between September 2004 and April 2005.

He told Sky News he has been amazed at just how drawn out the process had been, as the Government has fought to keep the memos private.

"There's a lot of talk and speculation about what Prince Charles writes to the Government about and I just think actually we should get to see those letters and be able to make up our own minds, whether or not we think he should be doing that and whether or not they're important," he said.

Last year, judges at the Court of Appeal ruled the Attorney General, on behalf of the government, had "no good reason" to stop the 27 letters from being released.

But in a final attempt to prevent their publication, the government has turned to the Supreme Court to ask them to overturn that ruling.

It has been argued that any perception that Prince Charles disagreed with ministers would be seriously damaging to his role as future monarch.

Prince Charles is well known for his strong opinions on a range of topics from the environment and farming, to complementary medicine and architecture, and he has always argued his campaigning is a catalyst for change.

But there are those who believe, as heir to the throne, he goes too far, potentially straying into party-political matters.

We know he has written to politicians and prime ministers for at least the past 40 years.

Paul Richards was a special advisor to a number of Labour MPs and saw the impact his letters would have.

He said: "It was treated as though it had come down from the mountainside and treated like holy writ, taken straight into the private office of the minister, put on top of the pile for the minister's attention and then interestingly acted upon very soon afterwards in a way that no other organisation I can think of would have the same sort of interest and then action."

It is unclear what the 27 letters are about but they were written to seven government departments, including the Cabinet Office.

Catherine Mayer, author of 'Charles - The Heart of a King', has spoken to MPs, friends and staff who have all received letters from the Prince, often delivered inside three envelopes for extra security.

She believes most of the memos may be fairly mundane.

She said: "For Clarence House, they are in a no-win situation here.

"If the letters come out clearly there will be some embarrassment relating to maybe a couple of them, if they do not it will look like they have had assistance to bury something, they can't win," she said.

Even if the Supreme Court judges rule in favour of The Guardian, it is unclear when the letters would be released.

However, whatever the judgement, the letters continue to hold a wider significance, representing the uneasy balance between a Prince's privacy and the public's right to scrutinise the man preparing to be king.