The tragedies that led Paul Getty to discover his mission in life: to give away his money

John Paul Getty Jr lived several lives, all of them eye-catching, all of them enigmatic, all of them tinged with the self-destructive madness that only the world's super-rich can inflict on themselves. The oil tycoon's son, who died yesterday at the age of 70, made an extraordinary and often painful transition from long-haired, drugged-out hippy to inveterate Anglophile and philanthropic country squire.

Like so many second-generation billionaires, Sir Paul dedicated his life to spending the family fortune rather than consolidating or expanding it. But unlike other children of famous fathers who struggled with the burden of their birthright and ended up drugged out, dissolute or prematurely dead, he managed to beat back his demons to become a generous patron of the arts and several unlikely and unfashionable causes.

He gave to the National Gallery, to the British Film Institute, to Lord's and the Marylebone Cricket Club. He took pity on the Conservative Party after its ringing defeats of 1997 and 2001. But he also made more discreet donations to more progressive social causes, most famously the families of striking miners during the 1984 stand-off between Arthur Scargill and Margaret Thatcher.

In his later years, he was celebrated for hobnobbing with Tory grandees, having a replica of the Oval cricket ground built on his 300-acre Buckinghamshire estate and hankering after a halcyon vision of rural England that had long since vanished, if it existed at all. Being granted British citizenship and giving up his US passport in 1997 was one of the proudest moments of his life.

All this was a long way from the chequered progress of his early years: the loving son who tried and failed to please his tyrannical father, the party addict who hung out with rock stars and glamorous women until alcohol and heroin proved their undoing, and the absentee parent who had to beg for the life of his eldest son after his kidnap by Calabrian gangsters.

For years, Sir Paul was a virtual recluse, battling the health consequences of his addictions at his London home in Cheyne Walk, and, later on, behind the walls of his Wormsley Park estate. But slowly he turned himself round, undergoing a series of conversions. With the help of his third wife, Victoria Holdsworth, he became a practising Catholic. Through his friend and Chelsea neighbour Mick Jagger he developed a passion for cricket. And, after the death of his grandmother in 1984, he gained access to his first serious chunk of the family fortune and decided it was his mission in life to give it to those who needed it more than he did. Asked to describe his occupation, he would always answer "philanthropist".

Throughout his life, his defining relationship was with his father, the distant, notoriously miserly John Paul Getty, who built his empire on "Oklahoma crude" and bought his way first into European high society and then into the highest echelons of fine art collection.

The younger Getty was actually born Eugene Paul, but changed his name to John Paul out of admiration for his father. (He later went by just plain Paul.) Both his parents went on to other marriages, however, and largely vanished from his life. He was brought up, essentially, by his paternal grandmother, Sarah, in San Francisco.

After brief stints at the University of San Francisco and in uniform during the Korean War, he married his college sweetheart, Gail Harris, and agreed to look after his father's business interests in Italy. But the oil industry didn't thrill him nearly as much as Rome's dolce vita that was hitting its zenith at the time. "It doesn't take anything to be a businessman," he told his father, quitting his job in favour of endless parties, kaftans, beads, sex, drugs and rock and roll.

According to his mother, Sir Paul longed to be "a character in a [F Scott] Fitzgerald novel", and he collected rich and eccentric friends, from Claus von Bulow and Gore Vidal to the Rolling Stones and Talitha Pol, a beautiful Dutch socialite who was the granddaughter of the artist Augustus John. In the late 1960s he divorced Gail, married Talitha, bought a palace in Marrakesh and had a son – his fifth child – whom he named Tara Gabriel Galaxy Gramophone.

The party came crashing down in 1971, when Talitha died, apparently of a drug overdose. John Paul Getty Snr was so appalled that he cut his son out of the family inheritance, forcing him to subsist on a trust fund from his grandmother, most of which went on child support, and the rest on rum and heroin.

When Sir Paul's eldest son, Paul III, was kidnapped on a Rome street in 1973, he was living in London and quite unable to meet the ransom demand of more than $3m (£2m). He begged his father for help but was turned down cold. "I have 14 other grandchildren. If I pay a penny of ransom, I'll have 14 kidnapped grandchildren," he was told. The old man softened after a part of Paul III's ear was mailed to an Italian newspaper but he forwarded most of the ransom money as a loan to his son, slapping 4 per cent interest on the return.

Even after this trauma, Sir Paul insisted that he still loved and admired his father and grew angry when anyone suggested the contrary. Still, the tensions between them remained. One of his first charitable acts on coming into his grandmother's fortune in 1984 was to give £300,000 to the Manchester City Art Gallery to prevent a Duccio crucifixion from being snapped up by the J Paul Getty Museum in Malibu – the cornerstone of the art empire founded by his father.

A decade later, he contributed a further £1m to keep Canova's The Three Graces at the National Galleries of Scotland, when it too was in danger of being shipped out to California. The director of the National Galleries, Timothy Clifford, almost blew the deal when he said Sir Paul was motivated by his bad relationship with his father. In a rare public statement, Sir Paul said: "This is not only untrue, but very embarrassing to myself and the museum." He came very close to withdrawing his offer.

Out of a fortune estimated at between £300m and £1bn, he gave away more than £100m over the past 19 years, including £50m to the National Gallery in London and £20m to the British Film Institute. He didn't like to draw attention to his philanthropy and kept very much to himself, especially in his final two years when he was undergoing regular dialysis and was largely confined to a wheelchair. His last real hurrah came in the summer of 2001, when he threw a lavish party at Wormsley Park.

Three years earlier, he had glowed with pride at Buckingham Palace on receiving his full knighthood after his acceptance as a British subject. Sir Paul had no doubt where he belonged. "When I heard the national anthem played, I felt very proud to be British – it's my national anthem now," he said. "I love Britain's way of life. I love its people. I love its history and I love its future."