Now the lid could be lifted on one of American’s most colourful families if her attempt to reveal the last thoughts of William Randolph Hearst is successful.

Patty and her cousin, William Randolph Hearst II, have brought an action in Los Angeles applying to make the tycoon’s will public, despite a clause that anyone who challenges its secrecy will be instantly disinherited. If they succeed, they will lay open the workings of one of America’s most revered business empires.

The Hearst Family Trust would have to reveal the full value of its assets, most of which are in Hearst Corporation, a media conglomerate that is steeped in history and includes newspapers, magazines and cable television channels. It is thought to be worth at least $18 billion (£9.4 billion).

Unlike Charles Foster Kane, Orson Welles’s thinly disguised portrait of him, William Randolph Hearst was the son of a multimillionaire senator from California. He took over his first newspaper, the San Francisco Examiner, at 23. Seven years later he broke into New York with the Morning Journal and began a circulation battle with rival mass-market publications. His paper’s sensationalised reporting of Cuba’s struggle for independence from Spain has been cited as a cause of the United States’s war with Spain in 1898.

Not satisfied with his media empire, which embraced newspapers, magazines and film companies, Hearst moved into politics, serving in the House of Representatives from 1903 until 1907. He failed twice to become the mayor of New York City and also lost the race to become its governor.

Hearst died in 1951, leaving instructions that the Hearst Family Trust should be controlled by five trustees from the family and eight from Hearst Corporation.

Heirs who are not trustees receive tens of millions of dollars a year in dividends from the corporation, but they will not gain control of the company until the trust is dissolved. According to Hearst’s will, that will happen only after the death of the last grandchild, who was alive at the time the tycoon died, an event that will probably not happen for another three or four decades.

The family was pitched back into the headlines in February 1974 when Patty Hearst, then 19, was kidnapped by the Symbionese Liberation Army, a Californian terrorist organisation. She took up arms with her kidnappers, helped to rob a bank and was captured and jailed a year later.

Anxious that other family members might be targeted, the trust was put under lock and key to protect the Hearst empire’s true wealth from being known and to hide the identities of its beneficiaries.

Ms Hearst, who was released from prison in 1979 and pardoned by President Clinton in 2001, says that she feels responsible for the will being locked away and wants to see it made public. “I feel very uncomfortable with this seal, partly because of the kidnapping, as though this is my fault,” she said. “I feel like these are public records. Why shouldn’t they be made public?”

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