Washington Post reporters Bob Woodward and Carl Bernstein had always said they would not reveal the identity of their Watergate source Deep Throat until he was dead.
'The guy they called Deep Throat', with daughter Joan
In the end, American journalism's most famous anonymous source did it himself.
Mark Felt, who was deputy director of the FBI during the scandal that brought down President Richard Nixon, came out in Vanity Fair magazine with the plain-spoken admission: "I'm the guy they called Deep Throat."
The magazine had spent two years at work on the story, its London editor told the BBC.
Even so, Vanity Fair could not be certain its story was right until Woodward and Bernstein confirmed it on Tuesday, Henry Porter said.
"A percentage of doubt in this case was reasonable," he said, although he added the magazine had "a huge amount of evidence".
In fact, the magazine had been approached several years ago by a friend of Mr Felt's family.
San Francisco lawyer John O'Connor contacted Vanity Fair editor Graydon Carter to say a client of his was Deep Throat and wanted to unmask himself in the magazine.
Mr Carter rejected the story because Mr O'Connor wanted the magazine to pay Mr Felt and his family for the story, the Washington Post reported.
Bernstein and Woodward kept the secret for more than 30 years
Mr O'Connor then looked into writing a book about Deep Throat, but ultimately came back to Vanity Fair.
When the magazine agreed to run the story, it assigned a team of about 15 journalists to work on it with Mr O'Connor, and went to extreme lengths to keep it a secret.
It even sent the magazine to the printer with a false headline on the cover.
Those kept in the dark included one of the magazine's own contributing editors - Carl Bernstein himself.
Woodward and Bernstein only learned of the story when Vanity Fair emailed them on Tuesday morning, shortly before going public.
"We felt that if we let Bob or Carl know, the Washington Post would be out before us," David Friend, the lead editor on the story, told the Post.
The 91-year-old Mr Felt had been mentioned decades before the Vanity Fair story as a possible Deep Throat.
"In fact, Felt was pretty much fingered in 1974 in a series of articles in the Washingtonian magazine - and I mean the evidence stacked up in the Washingtonian is very persuasive when you read it now," Mr Porter told the BBC.
But Mr Felt had firmly denied being Deep Throat many times over the years.
At one time, he said if he had been the secret source he "would have done better".
"I would have been more effective. Deep Throat didn't exactly bring the White House crashing down, did he?" Mr Felt told the Hartford Courant newspaper in 1999.
He reportedly only told his family in the past few years, and they urged him to go public.
End of a secret
Mr Felt was only one of literally dozens of Washington insiders to be a suspect.
Just about every whiskey-drinking, cigarette-smoking man close to the White House has been proposed since Hal Holbrook made the character famous in the film version of Woodward and Bernstein's book All the President's Men.
Candidates have included former presidential candidate Pat Buchanan - a young speechwriter in the Nixon White House - and even ex-President George HW Bush, the current president's father.
A four-year investigation by a University of Illinois journalism class named Fred Fielding, who was deputy White House counsel under Nixon.
Like all the other suspects, Mr Fielding denied it.
Only on Tuesday did one finally come forward.
Leonard Garment, a lawyer in the Nixon White House who published a book called In Search of Deep Throat, said it would be "a relief to everyone to have this settled".
But Washington Post columnist Hank Steuver disagreed, lamenting: "What's gone is the last best secret. What could be more of a let-down than finding out who Deep Throat is?"