By Kevin Anderson
BBC News website, Washington
These days in Washington, journalists protecting sources are sent to jail, former White House counsel and Watergate figure John Dean observes.
Deep Throat's leaks led to the resignation of Richard Nixon
But some 30 years ago two enterprising young reporters at the Washington Post helped topple President Richard Nixon in large part due to a super-secret source known to the world only as Deep Throat.
The source's identity is one of the most enduring mysteries and best-kept secrets in Washington.
The opening of the Watergate archives of Washington Post reporters Bob Woodward and Carl Bernstein has served as the latest pretext for another round of media-fuelled speculation over the identity of Washington's most famous inside source.
Few facts are known about Deep Throat, and Mr Woodward has promised to keep his identity a secret until after his death.
Of the facts that are known, we know that Deep Throat is a man, that he smokes and likes Scotch.
Other than the two reporters, only former Washington Post executive editor Ben Bradlee knows the identity of Deep Throat.
Woodward and Bernstein look at a display of their Watergate notes
Now, Woodward and Bernstein's Watergate notes, sold for $5m in 2003, are on display in Texas - all the notes apart from material on Deep Throat, that is.
Those notes are being kept at an undisclosed location.
The reporting team made the rounds on American cable channels and were peppered with questions trying to extract every last shred of information about Deep Throat.
But Woodward and Bernstein refused to renege on their promise.
Adding fuel to the fire is a column in the Los Angeles Times by former White House counsel John Dean, who says that sources have told him that Deep Throat is ill.
Mr Bradlee, the former Washington Post editor, has acknowledged that he has already written Deep Throat's obituary, Mr Dean said.
It must be said that apart from these tantalising morsels, Mr Dean remains in the dark.
He knows that it is one of his former colleagues at the White House, but he added: "I'll be damned if I can figure out exactly which one."
A Bush connection?
Adrian Havill had claimed in a 1993 unauthorised biography of Woodward and Bernstein that Deep Throat was a composite of several sources.
Mr Woodward has denied that theory.
An author says George HW Bush was Deep Throat
But now Mr Havill believes that Deep Throat is in fact George HW Bush, the father of the current president.
He made his claim on a journalism website last week, saying he came to the conclusion after recent events and a review of documents at the National Archives in Maryland
Why else would current president George W Bush, known to strenuously dislike the press, grant seven hours of interviews to Mr Woodward and urge his cabinet to cooperate, Mr Havill asked.
And the elder Bush had ample motivation to want to rat on Richard Nixon, the author said.
Nixon had dangled the prospect of a number of positions in the administration in front of Mr Bush in 1970s, including a place at the Department of Treasury or even as running mate in 1972, Mr Havill says.
Nixon reneged on these promises, giving Mr Bush reason to want revenge.
However, there are problems with this theory.
By Mr Havill's own admission, Mr Bush wasn't in Washington between 1971 and 1972. He lived in the Waldorf-Astoria in New York, where he served as US ambassador to the United Nations.
Deep Throat uncovered
And William Gaines, who led a four-year investigation into the identity of Deep Throat with his students at the University of Illinois, said Mr Bush didn't have access to the information that Deep Throat is known to have revealed.
Mr Gaines and his students used an unedited manuscript of Woodward and Bernstein's book All the President's Men and reams of public records including 16,000 pages of FBI records, much of them contained on nine reels of microfilm in the university's library.
They used a process of elimination by taking information linked exclusively to Deep Throat and cross referencing that with who might have had that information in the Nixon White House.
One study points to White House aide Fred Fielding as Deep Throat
Much of the information that Deep Throat provided to Woodward and Bernstein flowed through John Dean's office.
For instance, Mr Gaines points to an incident when President Nixon's domestic advisor John Ehrlichman told Watergate burglar Howard Hunt to leave Washington the weekend after the bungled burglary.
Only six people were known to have been involved, including Fred Fielding, Mr Dean's deputy.
And time after time, Mr Gaines and his students found that Mr Fielding was one of a handful of people at the White House with information linked to Deep Throat.
And the students believed that the reporting team might have protected Deep Throat in their reports.
They point to a story about Katherine Chenow, secretary to Howard Hunt and fellow Watergate burglar G Gordon Liddy.
She was vacationing in England at the time of the break-in.
John Dean dispatched Mr Fielding to bring her back to the US, in part so that she could be coached before being interviewed by the FBI.
Carl Bernstein wrote about this some five months later after obtaining her phone number.
However, he only said in his story that a member of John Dean's staff had brought her back to the US and did not mention Mr Fielding by name.
Ms Chenow, feeling that she might have been too candid with Mr Bernstein, had called Mr Fielding to discuss the conversation with him.
In notes obtained by the students, they found out that Mr Bernstein knew that the "member of John Dean's staff" was in fact, Mr Fielding.
"To omit the name from the story was the kind of care a reporter would take to coddle a friend and source," the students wrote.
Mr Fielding has denied being Deep Throat, but Mr Woodward has said that Deep Throat has lied to protect his identity.
For now, the mystery continues.
But if John Dean is correct, and Deep Throat is indeed ill, one of the greatest mysteries in Washington may soon be solved.