PRIX DE L'ARC DE TRIOMPHE:IN VINCENT O'Brien's official biography there is a photo taken at Longchamp after the first of Alleged's two Prix de l'Arc de Triomphe victories where a lot of faces seem to be behaving against type

For one thing Lester Piggott has a wonderfully unaffected smile on his face as he chats to the then President – every “No to Lisbon” voter’s favourite French baddy – Valery Giscard d’Estaing, whose normally patrician mien is softened by something approaching enjoyment.

Right next to the two of them is the late Vincent O’Brien, normally the most reserved of men, looking, well, pretty damn smug. Not that one could blame him.

Surrounded by symbols of La Belle France, right down to the policemen’s famous pillbox hats, O’Brien is surely entitled to feel a little warm with himself. He had, after all, just landed Europe’s most coveted race, and got a bit of his own back on the Arc as well.

In addition to Alleged (1977-78) the great trainer also won the great race with Ballymoss in 1958. But his Longchamp legacy probably lies just as much with the one that got away, the race in 1970 that presents so many parallels to tomorrow’s renewal.

Just like Sea The Stars, Nijinsky came to Paris with a perfect three- year-old record and on the back of a Triple Crown success in the Leger that had been achieved with such a swagger that many really did feel he was unbeatable: Except there hasn’t been a horse to look through a bridle that couldn’t be beaten.

O’Brien insisted to Piggott that he “must lie up” with the pace. Instead Nijinsky was fourth last with half a mile to go. Even so, he powered down the straight and looked to have grabbed Sassafras only to lug left in the dying strides and get beaten a head.

“The horse had shown Lester such tremendous speed in all his races that he felt he could pick them up whenever he wanted,” O’Brien later recollected. “But Longchamp is different.”

It sure is. So many great horses have sealed their reputation in the Arc but so many others have found it one ask too many. O’Brien’s other great classic star Sir Ivor couldn’t get to grips with Vaguely Noble in 1968. Troy could manage only third to Three Troikas in 1979. Generous was out of sight behind his old rival Suave Dancer in 1991.

Coming as it does in October means those with established reputations can go to the well once too often, while comparatively unheralded horses suddenly seem to burst into the limelight. Overall it is the supreme all-aged challenge in Europe and one which only five Irish-trained horses have ever managed to overcome.

Encouragingly for fans of Sea The Stars, one of them was Sinndar in 2000, the English and Irish Derby winner who John Oxx took to Longchamp via success in the Prix Niel. That is the classic French route to Arc glory, forsaking midsummer pots in order to bring a fresh horse to the party. Sinndar’s was a classic prep and the value of freshness was underlined as the Arc proved a race too far for defending champion Montjeu who looked so imperious just three months earlier in the King George.

One horse that completed a King George-Arc double in the same year was Ballymoss, O’Brien’s first truly top-class flat horse that overcame unsuitably soft ground conditions to win in 1958 under the legendary Australian rider, Scobie Breasley.

He later declared Ballymoss to be the best he had ever ridden and O’Brien remembered: “I’ve never heard anything to equal the reception he got. French, English, Irish and goodness knows how many other nationalities all paid tribute by surging around the horse. Ballymoss ought to have gone crazy but he could not have been less perturbed.”

Another Aussie, Bill Williamson, was on board Levmoss in 1969 but he travelled to Longchamp expecting to be an also-ran. Bred and owned by the McGrath family in Co Dublin, and trained by Seamus McGrath, Levmoss was Europe’s top stayer with wins in the Ascot Gold Cup and Prix du Cadran.

But up against classic stars like Prince Regent and Blakeney, as well as the star filly Park Top, Levmoss was dismissed as a 52 to 1 shot, a price Williamson for one agreed with. But after riding Vaguely Noble the year before, “Weary Willy” somehow brought off the double with Piggott again finishing too late on Park Top.

“I’ve had some good horses but I think this one takes the biscuit,” McGrath said afterwards. “In fact I know he does!”

Levmoss ended up at stud in France before dying in 1977, the same year that Alleged became just the sixth, and last, back-to-back Arc winner.

The Minstrel was the Ballydoyle Derby hero that year but later in the season the late-maturing Alleged went to Longchamp on the back of a controversial defeat in the Leger which failed to diminish O’Brien’s faith in the colt one iota. Recovering from his Leger disaster, Piggott controlled the race from the start and Alleged was never in danger from the New Zealand champion Balmerino. Twelve months later despite an interrupted preparation, he repeated the feat.

In the great pantheon of Ballydoyle champions over the years, Alleged can often be overlooked in the midst of all those Derby winners but the old master trainer never made that mistake: winning the greatest race in France even once takes an exceptional horse.

Sometimes hanging onto it can be just as nerve-wrecking.

Dylan Thomas was a worthy Arc winner two years ago but he was also lucky. Now the race is best remembered as a last-hurrah by Kieren Fallon before entering an 18-month drug ban purgatory. But the finish was hugely controversial in its own right.

By most readings of the French racing rules, Aidan O’Brien’s star should have been flung out in a stewards enquiry after veering right across Zambezi Sun and the other Ballydoyle hope Soldier Of Fortune. As the furore over the recent Dar Re Mi case proves, winners have been disqualified for a lot less but the Longchamp stewards’ lunch must have been particularly good that day.

Zambezi Sun’s rider Stephane Pasquier also played ball with Fallon in a big way, which was surprising considering the pair were hardly bosom buddies.

Dylan Thomas kept the race but those blindly betting that Sea The Stars is a “shoo-in” tomorrow should bear in mind the Arc is not the race it is because it’s some sort of gimme. Exclusivity doesn’t allow for that.