IF THE response to Diana, Princess of Wales's death was one of fleeting mass-hysteria, then Mohamed al Fayed's life over the past six years, by comparison, has been irrevocably gripped by the loss of his son, Dodi. In his belief that the couple suffered ''death by force'' and that MI6 was involved, he is unswerving. In campaigning to get a full investigation under way, relentless.

Following a newspaper report that Diana believed Prince Charles was plotting to kill her, it has been suggested that police may seek to question him. Whether Mr Fayed feels vindicated by these claims is unclear. Either way, his insistence that there would be strong interest in the results of an inquiry has gained strength.

Before he entered Edinburgh's Court of Session last month in an attempt to prove his son was murdered, he said: ''I am very hopeful and optimistic. I will be given the opportunity to discover what happened to my son and Princess Diana. I have chosen the Scottish courts because I have faith in the impartiality of the Scottish legal system. I will not rest until I get to the truth.''

Like the man himself, the real roots of his determination may remain a mystery. Despite his fame, verifiable details about his personal life are scarce, and summations of his character contradictory.

By the mid-eighties, spectacular al Fayed biographies had emerged. Most agreed that his great-grandfather had secured a fortune by growing cotton on the banks of the Nile and exporting it in his own ships to the Lancashire mills. The Fayed brothers inherited wealth, attended English schools, and were considered to be part of one of the most distinguished families in Egypt.

When the family uprooted to Britain, it was understood that the Fayeds were intimidatingly rich, and extraordinarily well-connected. It was said they kept close ties with the ruling family in the United Arab Emirates and the royal family of Kuwait, as well as business connections with the Sultan of Brunei.

It became virtually impossible to quantify the family's power. Mr Fayed was in business with his brothers, Salah and Ali, who were thought to help purchase land, run luxury hotels, oversee construction and oil businesses, and were into banking, property and shipping lines.

Mr Fayed's business sense was obviously inherited by his son Dodi, who suggested the family pay for the production of the film Chariots of Fire.

In 1985, it emerged that Mr Fayed was chasing the jewel in his business crown: Harrods. If he succeeded, it would, once and for all, make him part of the British establishment.

Mr Fayed was thought to hold the English in the highest esteem, and was later to launch an unsuccessful fight to be granted a British passport. He was said to have been cared for by an English nanny as a child. He sent his son to Sandhurst, and loved the idea of going about business in the country. ''The English are such gentlemen,'' he once told a reporter.

His relationship with the Scottish people got off to a shaky start. ''The Scots didn't believe that some bloody Egyptian would enhance their heritage when I bought a castle in Scotland,'' he spat in the mid-seventies, after procuring Balnagown Castle. ''But I spent a million pounds restoring it, and now they thank me for it.'' On becoming laird, he ordered a kilt, and said he looked like he was wearing a mini-skirt. Ten years later, he would be seen outside his Falls of Shin visitor centre on his 65,000 acre Sutherland estate handing out sweets, calling himself MacAlfayed, and claiming the Egyptians discovered Scotland.

His bid to buy Harrods was much less laughable. Britain's most famous department store was bought from Hugh Fraser, founder of House of Fraser, originally a Scottish institution, for (pounds) 615m. Some commentators were, at the time, outraged that the sale could be allowed to go so smoothly when so little was known about Mr Fayed's foreign

business deals.

A year later, Peter Wickman, writing for the Observer, was assigned to Egypt in search of the Fayed dynasty, and, famously, could not find it.

Fargally Pasha, the last surviving Egyptian cotton millionaire, said he had never heard of the Fayed's rival empire. Nor could Wickman find anyone who could talk about the many ships and hotels they owned.

It emerged that Mr Fayed's father, Ali Ali Fayed, was a primary school teacher who lived in a poor area in Alexandria. After leaving the local school, he worked as a sewing machine salesman for less than

10 Egyptian pounds a month, eventually making money with a furniture import company.

Three years later, John Plender presented The Harrods Sale, a Channel 4 documentary investigating the deal. What financial journalists had struggled to achieve over several years, the documentary achieved in an hour. Plender concluded that Mr Fayed and his brothers had duped the British press and the public about the origin and scale of their wealth. A 752-page report by the Department of Trade and Industry said Mr Fayed and his brothers ''repeatedly lied to us about their family background, their early business life and their wealth.''

Even without the Paris car crash, it has been suggested Mr Fayed would have been on bad terms with the establishment anyway. Over two decades, he engaged in a 14-year feud with business tycoon Tiny Rowland and entered a libel case with Neil Hamilton.

As it happens, he now has a true focus for his bile. His feelings on Tony Blair, who refused an investigation into his son's death, are clear. ''Tony Blair is a bloody idiot, failure as a lawyer, having nothing more in track record, right? You got Prescott. He was a waiter, maybe never gone to school and the f***ing guy, he's the deputy prime minister.''

Time is of the essence, and money is no consideration whatsoever. His legal team is led by Richard Keen, QC, the same man who secured the acquittal of Al Amin Khalifa Fhimah, a man accused of the Lockerbie bombing. Since 1997, he has spent more than (pounds) 3m on employing a team of investigators, scientists and lawyers, who have compiled a huge dossier on the accident.

''Princess Diana was the mother of the future king and the public are demanding the right to know the truth. When Dr David Kelly died, the government announced the Hutton Inquiry because of public opinion. Within 24 hours of Princess Diana's death, Tony Blair spoke of the

people's grief and the death of the People's Princess. The people now want to know the truth about how she died,'' he said.

For one so determined to unearth the truth, it is a considerable irony that Mohamed al Fayed's words are to be taken with a pinch of salt, not to mention a degree of sympathy.