Racing: The day Dettori's Magnificent Seven left the bookies in tears

However briefly he seduced outsiders into his sport, on that heady day at Ascot 10 years ago, Frankie Dettori gave them a lasting lesson in its least ephemeral qualities. Imagine some other unfathomable landmark: Tiger Woods, say, shooting 18 consecutive birdies. Anyone who witnessed such a feat would marvel with a sense of communal privilege. When Dettori won all seven races on one of the most competitive cards of the year, however, it was the most intense experience not only in his own life, but many others, too.

Never mind the pyramid of professional stories beneath each of those seven pinnacles - the years of patience and preparation vindicated by each horse that day. For many others to whom the day became unforgettable, 28 September, 1996 dawned with no more promise or interest than a thousand other Saturdays. Before dusk, Dettori would spin them faster and faster round his carousel, seemingly out of control, pivoting wildly round the molten fulcrum of his own instincts.

Just as Dettori, through the afternoon, gradually harnessed himself to some intuitive momentum, beyond his own skill and ambition - everyone agrees he would never have won the seventh race had it been the first - so those with fortunes at stake became helpless, stricken, sick to their stomachs. The ordinary rules of engagement between bookmaker and punter crumbled into anarchy. And, when Dettori deliriously crossed the line a seventh time, with Pat Eddery in blazing, resentful pursuit, he completed an incalculable rout.

It was the Mug Punter's revenge. At 25, this effusive Italian was the natural focus of any impulsive bet. And none could be more frivolous than the blind combination of all seven of his mounts on a day such as this.

True, Gordon Richards once went through a six-race card at Chepstow, part of a spree of 12 consecutive winners over three days. But this meeting at Ascot, as will be seen again today, was the sort where any jockey would settle for one winner. As Dettori himself said that morning: "I could have an each-way chance in the first, and I may win the third."

Mary Bolton was immune to such pragmatism. She and her husband, John, had come up to London from Somerset to celebrate their wedding anniversary. She was to spend the day shopping, while he went to Ascot. To give his wife an interest, John made her a present of a bet at Ladbrokes in Dover Street, Mayfair. She elected a permutation of Frankie's mounts, including a £5 each-way accumulator. "It was because of his character," Mary explained later. "All his smiling and silly nonsense when he wins."

Hers was just one of dozens of similar stories, up and down the nation. Many, inevitably, were poignantly mirrored by the disabled man who combined the first six, before changing his mind and ripping up his betting slip; or by the cleaner who had 50p on each of the seven. She collected £19. Had she added a 50p accumulator, she would have won £12,047.50 at starting prices, and around £120,000 if taking the morning odds.

In turn, the difference between those two payouts would become a gripping sub-plot. Gradually, the High Street betting shop chains realised that they were horribly exposed. After Decorated Hero won the fourth, their liability managers began to sweat. After Fatefully won the next, off-duty bosses started to call in. In the starting price system, the tail wags the dog. Off-course bets are settled at the final odds in the racecourse betting ring. The shop chains protect their own position by "sending" bets into the ring, so forcing down the price about a particular horse.

When Lochangel won the sixth, a £1 accumulator was worth £8,365.50. That sum would now run on to Fujiyama Crest, the animal happily innocent of his role in the drama developing around the final race. He had been available at 12-1 in the morning. Those who had lacked the prescience to take those odds would have their bets settled at starting price. For the off-course market, it was imperative to crush the odds against Fujiyama Crest.

And then something unaccountable happened. The mechanics of the system, a daily reflex of market forces, suddenly broke down. Bookmakers in the ring realised that they could lay 2-1 against a horse whose chance in reality was closer to 12-1. And flesh and blood took over. Instead of meekly cutting the odds lower still, they laid Fujiyama Crest for every penny they had, or thought they might have, if they sold their houses, cars and dependents.

That stand immeasurably raised the stakes on Fujiyama Crest. Barry Dennis, the egregious ring bookmaker, laid the horse to lose £23,000. During the previous 30 years, his biggest loss in one day had been £5,000. Even watching the race, he remained convinced he had done the right thing. As Dettori made the running, he waited for the inevitable challenges.

He told Graham Sharpe, author of The Magnificent Seven, what was going through his mind: "Don't panic, something is coming on the outside - this is going to beat him. I knew he couldn't ride all seven, it isn't possible. Half a furlong out - I do not know the challenger but he simply must get up. Twenty yards to go. Reality - it is not going to get up. Frankie's done it. I stood on my stool, staring, not hearing a thing, in a trance."

Dennis drove home in silence, his staff too frightened to speak. When he got home, his wife greeted him cheerily. "Hello darling," she said. "Good day?" Dennis told her Dettori had ridden all seven winners. " Fantastic!" she said. "What a great achievement." Dennis collapsed into a chair, sobbing.

And he had got away lightly, compared with some. Gary Wiltshire went on to Milton Keynes greyhounds facing liabilities of £800,000. "The first bet I took was a pound," he said. "It was going to be a long way back."

Ladbrokes had inoculated themselves against such unpredictable dramas with a maximum payout of £500,000. The Boltons were due £900,000, but were not too despondent, having initially persuaded themselves that they had won only £300,000. Fred Done flashed a message on to his betting shop screens: "Reward, dead or alive: good-looking Italian kid, last seen in Ascot area."

At the precise moment when Fujiyama Crest passed the post, the clock stopped in a north London betting shop. The proprietor never changed it. He does not need anniversaries to remind him what happened that day.

The Magnificent Seven Where are they now?

By Sue Montgomery

* WALL STREET Odds 2-1

A three-year-old when winning the Cumberland Lodge Stakes, he is the only one of the seven not still alive. He raced once more, when eighth in the Breeders' Cup Turf, but died after a suffering a bout of colic in Dubai that winter.

* DIFFIDENT Odds 12-1

The Diadem Stakes was the best of Diffident's seven wins and at the age of 14, the son of Nureyev is now a star stallion in India. He stands at the Poonawalla Stud, at Pune, where he has sired local Guineas and Oaks winners.

* MARK OF ESTEEM Odds 100-30

Mark Of Esteem's defeat of Bosra Sham in the Queen Elizabeth II Stakes made him the best in Europe that year. Now 13, the Darshaan horse has made an excellent fist of his second career at Darley Stud, sire of this year's Derby winner Sir Percy and top sprinter Reverence.

* DECORATED HERO Odds 7-1

Decorated Hero carried top weight of 9st 13lb in the Tote Festival Handicap. The Warning gelding, now 14, raced for two more seasons - winning 14 of his 33 races - before finding a home at the British Racing School in Newmarket, where he helps teach aspiring Dettoris.

* FATEFULLY Odds 7-4

After taking the Rosemary Stakes, Fatefully won once more and is now a broodmare for Gainsborough Stud. She has produced six foals, including Nassau Stakes winner Favourable Terms. Now 13, she is pregnant to Selkirk.

* LOCHANGEL Odds 5-4

Lochangel scored her maiden two-year-old victory in the Blue Seal Stakes and went on to win the Nunthorpe Stakes at four. The daughter of Night Shift has not been as good as a producer for Littleton Stud, with one minor winner. She is due to Danehill Dancer.

* FUJIYAMA CREST Odds 2-1

Fujiyama Crest had a chequered career after winning the Gordon Carter Handicap, descending to claiming company after several changes of stable. The 14-year-old gelding, whose eight wins included one over hurdles, is now happily retired as the Dettori family pet.

'9-4 Fujiyama and 9-4 me for the Job Centre'

Gary Wiltshire: The Bookie

A hulk of a man, this on-course bookmaker faced several lean years after taking a dauntless stand against a flood of money from betting shop chains for Dettori's seventh mount, Fujiyama Crest. Wiltshire stood next to his pitch on the rails and bellowed: "9-4 Fujiyama! And 9-4 me for the Job Centre!" Later, he explained: "The odds were miles wrong. I was laying 2-1 about a horse I made a 10-1 shot."

He faced ruin, owing over £800,000. He sold his house and cars and scraped money together selling Christmas paper in Oxford Street. After that he " worked every hour God made", betting at six race meetings and six dog tracks every week, and "settled every bet". He vows he would do the same again.

Darren Yates: The Punter

His joinery business in Morecombe, Lancashire, was in trouble, and his wife had insisted that he end his compulsive habit of backing Dettori. Yates had reluctantly agreed, but secretly staked £67.58 in combining all seven of Dettori's mounts.

Yates spent much of the afternoon playing centre-half for his local football team. After a 4-0 hiding, he popped into the pub and discovered that Dettori had won the first four races.

By the end of the afternoon, he had won £550,000. In a good week Yates earned £300, and had just been refused a building society loan. He had feared that he would have to lay off his six staff.

He has since doubled the size of his business and moved house.

Magnificent Seven: How Frankie Dettori Achieved the Impossible by Graham Sharpe published by Aurum at £7.99. ISBN 978 1 84513 162 3