A self-made billionaire who started off quarrying cement from his family farm in Co Fermanagh in 1973 with a £200 loan, Sean Quinn has suffered a huge £800m loss at Anglo Irish Bank. John O'Keeffe on where it leaves the very private Quinn family

Depending on who you believe, Sean Quinn is either one of the most astute businessmen that this country has ever produced or an uncomplicated quarryman who has got ahead of himself and is now about to suffer one of the greatest financial free-falls that this downturn can offer.

The success of the Quinn Family Group has been well documented and has held the attention of business journalists in recent years. Observers can rest assured that, should the portents of doom prove correct, any cataclysmic fall from grace will be met with even greater interest both here and abroad. The story over the last week has, after all, not been good for the group, which is estimated to be nursing an £800m loss from Sean Quinn's 15% leveraged derivative position in Anglo Irish Bank.

He has said that he will continue to tough out the market downturn and convert his contracts for difference (CFD) into ordinary stock. CFDs allow investors to buy an interest in a stock for an initial outlay of as little as 10% of its market price. However, when share prices fall, the holder must then cover the losses from their CFD provider. Nice work if you can get it. The problem is, sometimes it can get you first.

Amid all the media commentary about Sean Quinn's well worn path to riches (from the paternal gift of a gravel pit to his position last year as the world's 177th richest man, and the UK's 12th, with a business value then of £3.5m), little is known about the family who surround him. He "jealously guards" his family privacy and, as he rarely gives interviews himself, commentary on his family has invariably remained vague.

His brother, Peter Quinn, is regarded as the real strategist of the family and not a man averse to risk-taking. As GAA President in the first half of the Nineties, he is credited with being the brains behind the commercialisation of Croke Park and, indeed, the GAA as an organisation. Unafraid to speak his mind, a year ago he attacked almost every institution in the State while also having a go at what he called the "non-risk taking dead hands" in Ireland.

A chartered accountant by profession and a significant shareholder in the Quinn Group, Peter once described his brother Sean as "an eternal optimist, which is necessary in business". The next few months will prove instructive as to whether this optimism was groundless or not.

Sean Quinn's wife and five children are the people who have been most sheltered from the public eye, yet they are also riding the current financial tsunami that has beset the group.

In fact, an internet search on any of his offspring's names — Aoife, Ciara, Sean Jnr, Colette or Brenda Quinn — reveals little more than unrelated Facebook entries or doppelgangers who are experts in golf and pottery. To be central cogs in the Quinn family group and yet avoid internet detection may prove to be among family members' greatest achievements.

His wife Patricia (55) owns 9.4% of Quinn Group — which, even at its current market valuation, would make her a paper millionaire many times over. All children are now believed to work within the group in various capacities and they hold various stakes, though each will almost certainly end up with a fifth of its assets in due course.

Ciara (31) is the eldest and perhaps the most well known offspring, having married Blanchardstown solicitor Niall McPartland in November of last year in the media glare. She holds a whopping 22.7% share of the company but, like her father, would appear to choose frugality over excess. Her wedding reception was held in the family-owned four-star Slieve Russell Hotel and, despite the presence of two brand new Rolls Royce Phantoms (costing £280,000 apiece), much to the disappointment of the papaparazzi and onlookers, ostentation was not the order of the day. She is a director of Quinn Hotel Properties and is thought to have a major input into the nine hotels in the Quinn Hotel Group.

Sean Jnr (29) holds 20.3% of the company and is considered by many to be the heir apparent. Indeed, he may be one of the few family members able to raise a smile as he is listed as having only one directorship in the Republic — in the Quinn Insurance Group, which last week came out as a winner in the risk equalisation legal battle.

He lives in a penthouse apartment in the exclusive Farmleigh Woods, which adjoins Farmleigh House in Dublin and where until recently three-bed penthouse units were selling for prices from £1.8m. Then there is the small matter of a golf course. He also owns The Belfry, one of Britain's most exclusive and historic golf venues. In short, life's good.

Colette (32) holds 6.8% and directs the pub and hotel companies and is listed as having 13 directorships within the Republic.

Aoife (26) has the smallest stake of 6.7%, according to company records, but even after the battering the group has taken since last week, this represents more than £160m. She is also a director of the Holiday Inn in Nottingham, valued at about £6.4m.

Youngest child Brenda has a 20% share of the company held in trust by her parents. All the Quinn children are believed to have further significant assets outside the main group.

Commentators have noted that the family could suffer huge financial losses and still have a war chest that most of us could only dream of, but to Daddy it was never about that; for him, creating jobs remains the priority.

"The more you have, the more you want and the more you expect," he said in a recent interview, adding that when he started in the business he used to get excited when he saw his only lorry on the road. If less is indeed more, then Quinn and his family may yet have even better days to come.

Notwithstanding what many regard as the ill-timed investment in Anglo Irish Bank, it is said that Sean Quinn can read financial statements better than any accountant. Write the Quinn family off at your peril.