George Bernard Shaw is said to have remarked after spending time at the enormous castle built by the American newspaper magnate William Randolph Hearst in California, that it was what God would have built if God had had the money.

Constructed between 1919 and 1947 for an estimated $40 million, the Hearst Castle at San Simeon was the centrepiece of a 250,000-acre ranch reaching to 2,000 feet above the Pacific Ocean midway between Los Angeles and San Francisco. It comprised the Casa Grande (Big House) and a crescent of adjoining buildings facing the ocean, the sun or the Santa Lucia Mountains. Its 165 rooms contained Renaissance artwork and medieval furniture shipped from Europe. They overlooked 127 acres of gardens, terraces, pools and walkways.

San Simeon was Hearst’s primary residence for most of his adult life, but he also owned a million acre ranch in Mexico; a 67,000-acre estate including a mock Bavarian village in northern California; a large house on Lexington Avenue and other properties worth $50 million in Manhattan, New York; a home in San Francisco; a Norman castle in Wales and a Georgian mansion, Murrough House, on the edge of Galway Bay.

The only child of a father who was usually absent prospecting successfully for gold or silver and a former schoolteacher mother, Hearst had an Irish-Catholic governess, Eliza Pike, who also served as his wet-nurse until he was aged 14 months. She had him baptised secretly while his parents were away from home.

By his mid-teens he had accompanied his mother on two grand tours of Europe, during which he was horrified by the poverty that he saw on the streets of Dublin and blessed by Pope Pius IX at the Vatican during a private audience. His later penchant for owning castles was sparked by a visit to Windsor Castle outside London.

After being expelled from Harvard University he persuaded his parents to give him ownership of the San Francisco Examiner newspaper, on which his father has lost $250,000 while campaigning successfully for election to the US Senate. He revolutionised the Examiner and made it the prototype for the 31 other newspapers that he bought or established in New York, Chicago and 17 other US cities. By 1925, one in every four American families was reading a Hearst newspaper.

He used the Examiner to incite war between the US and Spain over Cuba in 1898. Circulation wars with rival publisher Joseph Pulitzer spawned downmarket journalism (called the Yellow Press after the colour of the papers’ cartoon characters). Some also blamed the wars for giving Chicago its notoriety for murderous gang battles.

Hearst also owned popular magazines including Cosmopolitan and Good Housekeeping. Sean O’Casey and Frank O’Connor wrote for his flagship magazine, Harper’s Bazaar, when it was edited by Dubliner Carmel Snow. Hearst sent future US president John Fitzgerald Kennedy to Europe as a roving reporter as a favour for JFK’s father, Joseph Kennedy.

Marriage to Millicent and the birth of their five sons did not inhibit Hearst, aged 55, from embarking on a live-in affair with silent screen actress Marion Davies, aged 21, that endured for the rest of his life.

Hearst built Davies a 14-room “bungalow” on MGM’s Culver City lot and a $7 million beach house at Santa Monica, whose diningroom, reception room and drawingroom he imported intact from Burton Hall in Co Clare. While living with Davies for 33 years, he remained friendly with his wife and bought her an apartment on Park Avenue, New York, and a summer place on Long Island.

Cork’s Kilmainham: ‘It’s a 1916 site because Thomas Kent was executed there’

Hearst was mocked mercilessly and inaccurately in the 1941 Oscar-winning Orson Welles/RKO film Citizen Kane. His later years were blighted by Davies’s daily drunkenness. He cried bitterly when they left San Simeon together for the last time in 1947 because of his failing health. He died in 1951, leaving a personal estate worth $59.5 million and publishing assets of $160 million.

San Simeon is now a US historical monument and State Park. Hearst consigned his Galway Bay mansion to Galway Corporation in 1937, along with the city’s 16th century silver sword and mace that he had bought at auction in London.

The first of many Hearst biographies was published in 1928, 23 years before his death. It was broadly favourable, sold well and was given the prime review spot in The New York Times. Hearst declined to read it. He said: “If it doesn’t tell the truth it will make me mad, and if it tells the truth it will make me sad.”