Psst. Don't let on, but you won't believe this. There are people out there who think Istabraq isn't a certainty tomorrow. In fact they actually think, and I know this is hard to credit, they think he might even be vulnerable. They're even looking for something to beat the great horse! And these people aren't even psst!

You see there's something about the AIG Europe Champion Hurdle and Istabraq. And that something is that he always wins it. He's won it for the last three years, every time he's run in it. In 1999 he was actually as long as 8 to 15. Except there was another rather special horse in the race that day called French Holly, which explained the price.

There's no French Holly-type talent against him now. This time Istabraq's got an entirely home-trained opposition, and not many of them. Ordinarily this should be a shoo-in but what the psst brigade are banking on is that tomorrow's race is out of the ordinary. And in one sense they have a point.

For one thing, the AIG was not even supposed to be on Istabraq's programme this year. Aidan O'Brien didn't make a secret of that. Istabraq was going to have a quiet time of it this winter. One run and then the edges would be honed at home for that remarkable attempt at a fifth consecutive Cheltenham festival victory. But it's that one run which has produced the doubts.

It's not that Istabraq fell. Every horse can misjudge things or make a mistake. Even Arkle did that. It's just that hurdle racing's modern Arkle actually looked tired before he collapsed in a heap. For a horse renowned for his style that was a shock, and it's where the whisperers are rooting for vulnerability. The bad news for them, however, is that the trainer of one of Istabraq's main opponents tomorrow thinks they're delusional.

"Vulnerable?" Dermot Weld repeats. "Istabraq? No. Personally, I don't think so." For the worldy and urbane Weld to be even momentarily stumped takes a lot of doing. It's not as if he will ever underestimate his own chance in any race or that his horse is some sort of plodder. Stage Affair actually gave Daylami a race of it one day up the Curragh for Chrissakes. It's just that Weld has seen enough of Istabraq to know better. He makes no bones about it.

"Istabraq is a superb racehorse, just a brilliant racehorse," he says simply. "And he's a superb hurdler."

The question how come he fell if he's such a good jumper is swatted away like an irritating but irrelevant insect.

"Some day he was always going to make a mistake. Nobody is invincible and you'll probably find he will be even better now than he ever was. This horse is obviously very brilliant and very intelligent. He will have learned from the fall. And you can be sure he will have been very well schooled since then," Weld says.

Having blown the front-line argument raised by the Psst heads, Weld doesn't even allow them to hold on to the weakish card that Istabraq's confidence might have been hit by the fall.

"Loss of confidence is more a factor with a young horse than with a horse like Istabraq. I just think he was tired the last day. I've read a report where Aidan said he thought the horse was lazy, but for me he was tired when he fell. The ground was very testing, he hadn't run in a long time and I think the whole thing will have sharpened him up," Weld concludes.

There's an obvious question in the circumstances about why bother to take the favourite on at all, but the quick answer to that came in that New Year's Eve race. In racing, nothing is too predictable. Istrabraq might have hit the deck but Stage Affair travelled brilliantly throughout that race, and the general view was that it was the gluepot ground rather than Moscow Flyer that eventually kept him out of first place.

"On better ground I would expect Stage Affair to beat Moscow Flyer. Stage Affair has won on heavy but on the flat he always showed he was most effective on fast ground. He has always been a good horse, but if it really rained before Sunday he would have his work cut out. Moscow Flyer is a very underestimated horse," argues Weld.

"This is a £100,000 race with a lot of prestige, excellent place prizemoney and if you're not in, you can't win. Having said that, if Istabraq is the horse we all know him to be, he will show why he is a 1 to 3 favourite."

For Istabraq's colossal fan club, such confidence is music to the ears. It's certainly more agreeable than the whispering chorus, and the whole thing is probably certain to end up in the number one spot anyway.