The new BBC2 series Watergate offers a rare view of a president with his guard down, chatting freely with advisers. Nixon knew that the tapes were rolling, but he thought no outsider would ever hear them. Fatally for his presidency, when their existence was revealed he chose not to destroy them - then failed in his attempts to keep them from the courts.
They contained more than enough to seal his destruction.
It would be wrong, however, to conclude that all the Nixon tapes are now public property. More than 4,000 hours were recorded between 1971 and 1973, but 20 years later only 63 hours of this material have ever been made public.
This is because, as he worked assiduously at his rehabilitation in the years after his fall, Nixon fought through the courts to prevent the release of any further tapes. And though Nixon is now dead, Nixon's lawyers say that the ex-president's estate - meaning his daughters Tricia and Julie - will carry on the fight. It may take new judicial interpretations, perhaps a new law, to sort it out.
Just a year ago, Nixon's lawyers gained an injunction to prevent the National Archives - which holds all the tapes - from releasing a batch of Watergate-related recordings covering the crucial months of July and August 1972. Days before Nixon died, it filed a motion asking that the block on release should be made permanent. Since his death, the question has arisen of whether the right to privacy extends beyond the grave. The National Archives has taken the initiative with a proposal to enable the public to buy copies of the tapes that have been released for a nominal charge, but the Nixon camp seems certain to fight.
A year ago, despite a battery of Nixon objections, a batch of Watergate-related tapes from May and June 1972 was released. Apart from the relatively small number of tapes that Nixon was forced to hand over before he resigned, these are the only recordings to have been made public.
They are scarcely less damaging to Nixon's reputation than the 'smoking gun' tape that toppled him by revealing his involvement in the Watergate cover-up.
They reveal, for example, Nixon's bid in May 1972 to exploit the attempted assassination of the Alabama Governor, George Wallace, by smearing his Democratic opponent for the presidency, George McGovern. In a conversation with his hatchet man, Charles Colson, Nixon suggests that they arrange a 'plant' of pro-McGovern literature at the arrested gunman's lodgings. This was thwarted only because the FBI had already sealed the lodgings.
What other dark secrets may be captured on tape? Two suggest themselves.
The first concerns the billionaire recluse Howard Hughes, who was giving money in 1971 both to the Nixon re- election campaign and to the Democratic Party's National Chairman, Larry O'Brien.
It has been argued that O'Brien might have had some Hughes 'dirt' on Nixon, and that this may have been one reason why the president's men were sent in to bug O'Brien's Watergate office.
By the same token, much of the ruthless Indo-China decision-making, as well as secret diplomacy for the summitry with China and the Soviet Union, fall within the tape period. No wonder historians, such as Stanley Kutler of the University of Wisconsin, are itching to get their hands on them. Mr Kutler has taken out a civil suit against the National Archives in an attempt to compel release of the tapes.
Whether we will ever see or hear this material is open to doubt. Even if the privacy question is resolved in favour of release, US laws, contrary to British imaginings, do not allow open season on government secrets. In the case of the Presidential Recordings and Materials Preservation Act the restrictions can be severe.
This Act was passed in 1974 specifically to prevent Nixon from destroying the tapes. During the Watergate crisis he had been forced to hand over a total of 77 tapes. But when he resigned, he intended to take the rest with him to California, until Congress stepped in, passed the Act and had the tapes sent to the National Archives.
Under the Act, the legal status of the tapes is anomalous. Nixon's death only complicates matters.
In principle they now belong to his daughters, but what they have inherited in practice is only the 'compensation value' - the sum that the courts must eventually decide is due to the Nixon estate in compensation for the government retaining his property against his wishes. This could turn out to be a lot of money.
Who controls the tapes is another matter.
The Act leaves them with the archives, specifying that the public has no access to private or personal materials - a term that embraces 'private political associations', which have no connection with Nixon's constitutional or statutory powers or duties.
Does this mean that this material - 775 hours out of the total 4,000 - should simply be given to Nixon's daughters? The National Archives says no. When Nixon was still alive, it offered to give him copies of the private and personal tape segments, but he demanded that the material be removed from the original recordings. The National Archives refused on the grounds that this would have been contrary to its duty to preserve historical material.
Sorting all this out will keep the courts busy for years, and Richard Nixon, from beyond the grave, may yet pull off his ultimate cover-up.
Fred Emery's book, 'Watergate - the Corruption and Fall of Richard Nixon' is published by Jonathan Cape, pounds 20. The Watergate television series begins tonight on BBC2 at 8.50.Reuse content