On May 31, 2005 one of Washington's best-kept secrets was revealed.

Vanity Fair magazine identified a former top FBI official named Mark Felt as Deep Throat, the secret source high in the U.S. government who helped Post reporters Bob Woodward and Carl Bernstein unravel the Watergate conspiracy. Woodward, Bernstein and the paper's editors confirmed the story.

"Felt's identity as Washington's most celebrated secret source had been an object of speculation for more than 30 years," wrote Post reporter David Von Drehle the next day.

The reporters had written about their trusted source in their best-selling 1974 book, "All the President's Men," and the 1975 movie of the same name dramatized his sometimes cryptic advice about how pursue the connection between the Nixon White House and a crew of seven burglars caught in the offices of the Democratic National Committee on the night of June 17, 1972. His true identity, the object of "countless guesses" over the years, remained secret until Vanity Fair's story. "I'm the guy they call Deep Throat," Felt told members of his family.

The day after the story broke, Woodward wrote a first person account of his relationship with Felt, which began with a chance encounter between a junior naval officer and a wary bureaucrat in 1970. Woodward cultivated him as a source. When the Post began to pursue the Watergate story, Woodward relied on Felt for guidance.

In May 2005 Vanity Fair magazine revealed that Mark Felt, pictured above with his daughter, was the source referred to ad "Deep Throat." The former No. 2 official at the FBI secretly confirmed to Woodward and Bernstein what they discovered from other sources in reporting on the cover-up.(AP)

"I was thankful for any morsel or information, confirmation or assistance Felt gave me while Carl and I were attempting to understand the many-headed monster of Watergate. Because of his position virtually atop the chief investigative agency, his words and guidance had immense, at times even staggering, authority," Woodward wrote.

But as The Post noted, Woodward and Bernstein also "expressed a concern that the Deep Throat story has, over the years, come to obscure the many other elements that went into exposing the Watergate story: other sources, other investigators, high-impact Senate hearings, a shocking trove of secret White House tape recordings and the decisive intervention of a unanimous U.S. Supreme Court."

"Felt's role in all this can be overstated," said Bernstein, who went on after Watergate to a career of books, magazine articles and television investigations. "When we wrote the book, we didn't think his role would achieve such mythical dimensions. You see there that Felt/Deep Throat largely confirmed information we had already gotten from other sources."