After a decade-long legal battle, a series of secret letters between Prince Charles and former British prime minister Tony Blair have been revealed, providing an insight into the halls of power.

The 27 letters, which have become known as the “black spider memos” because of the prince’s scratchy handwriting, were written between 2004 and 2005.

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In the correspondence to Mr Blair, the Prince of Wales expressed his concerns over problems facing dairy and beef farmers, as well as the delay of surveillance aircraft to British armed forces.

The 66-year-old also expressed a keen interest in health and argued against strict herbal medicine laws which “effectively outlawed the use of certain herbal extracts”.

The letters threatened to undermine the prince’s position of political neutrality. Photo: Getty

The letters also revealed Prince Charles has a soft spot for the “poor old albatross” and was keen to stop the overfishing of one the seabird’s food sources.

“I particularly hope that the illegal fishing of the Patagonian Toothfish will be high on your list of priorities because until that trade is stopped, there is little hope for the poor old albatross, for which I shall continue to campaign …”

Mr Blair’s replies show a fondness between the two men, with the former leader signing off his letters with “yours ever, Tony”.

The Guardian newspaper applied for the letters to be published under freedom of information laws, but the government fought against the release, saying they would undermine Prince Charles’ “position of political neutrality”.

In a statement, the prince’s private office, Clarence House, said the release of the letters would only inhibit the Prince of Wales from expressing his concerns in the future.

“The Prince of Wales cares deeply about this country, and tries to use his unique position to help others.”

“Over the past 40 years in his role as Heir to The Throne, The Prince of Wales has visited countless places and met numerous people from every walk of life. He carries out over 600 engagements a year.

“This gives him a unique perspective, which has often led to him identifying issues which he believes he, or his charities, or his other connections, can help address.”