Newly released letters from Prince Charles to Nancy Regan detail their 40 year friendship, revealing his struggles following his divorce from Princess Diana and his devastation after the death of his beloved grandmother.

The letters, part of Mrs Reagan's private collection, were released to the Ronald Reagan Presidential Foundation and Library following her death in March 2016. 

But only now have the letters, catalogued by archivists working on the library collection, been public.

After sitting next to each other at a White House dinner in 1981, Charles wrote that he was sold on the First Lady. "I am a devoted admirer for life!", he said.

Over the next 40 years, they wrote to one another regularly and shared intimate details of their lives.

In a letter dated June 21, 1992 barely six months before they announced their separation, Charles wrote to "my dear Nancy": 

"One day I will tell you the whole story. My problem is it is so awful and so extraordinary that very few people would believe it... It is a kind of Greek tragedy and would certainly make a very good play!"

It was weeks after the tell-all book by Andrew Morton, Diana: Her True Story, which detailed Diana's bulimia, suicide attempts and Charles' affair with Camilla, was published. 

Another of the letters, obtained by The Mail on Sunday, reveals a happier moment in the tumultuous marriage.

It was 1985, when Charles and Diana visited the United States and attended a gala with the Reagans.

During the "wonderfully relaxed" visit Charles reveals how dazzled Diana was by her famous spin on the dance floor with John Travolta.

"Diana still hasn't got over dancing with John Travolta, Neil Diamond and Clint Eastwood in one evening not to mention the President of the United States as well!," Charles said.

In another letter from June, 2002, Charles shares his grief about the Queen mother's death with Nancy.

"I fear it has not been very easy to cope of late," he admitted. "I have dreaded her eventual departure and now she leaves an enormous chasm in my life.

"However, she also leaves behind the most wonderful legacy of unbelievably happy memories… Oh, how we shall all miss her and everything she stood for..."

In a separate Mail on Sunday story, Camilla spoke of having to hide out when her long-term affair with the Prince was discovered.

"I couldn't really go anywhere," she told the publication.

"It was horrid. It was a deeply unpleasant time and I wouldn't want to put my worst enemy through it."

After briefly dating in the '70s, Charles admitted in his 1994 biography that they reignited their affair in 1986. Camilla and Charles married in 2005.

Fairfax Media