For many, the lure and charm of jump racing lies in the longevity of its stars, but there is no denying the frisson felt when that established order is challenged. Saturday at Chepstow was enriched by departure from the predictably mighty return of Paul Nicholls's string into a tale of two Jacks - one horse, one jockey, both bound for great things.

Until the spring, few would even have heard of Crack Away Jack, nor of Jack Doyle. Gangly young things, the both of them, and difficult to judge their potential. But Emma Lavelle thought she knew and, now, her chocolate-box yard in rural Hampshire has the excitement and anticipation of two potential champions.

Crack Away Jack gave Lavelle, 35, her first Cheltenham Festival winner in March and he is now as short as 8-1 for the Smurfit Kappa Champion Hurdle after a smooth comeback win. If he still has some growing and filling out to do, the same is hopefully untrue of his jockey. At 19, Doyle stands 6ft 2in tall, surely the one barrier to a golden future.

Indeed, equally as striking as his composure on the big-race winner was his earlier win on Seymar Lad.

It was not just that he rode the horses quite differently but the fact that he sweated down to 9st 11lb to initiate Lavelle's lucrative double. “I felt sorry for him,” the trainer admitted. “But I think he's got hollow legs.”

It was almost a decade ago, when Doyle was still in short trousers, that Lavelle first encountered him. “One of the first horses I bought when I started training came from Jack's father, Pat. I went over to Co Tipperary and remember him trotting off to school. I followed his progress in Irish pointing and I'm encouraged that Pat is tall and skinny, too, so hopefully the genes will help keep Jack light.”

There is still a gawky innocence to the features of the jockey unsurprisingly known as “Legs” but a few more insights come from his page on Bebo, the social networking site. Aside from saying he has no tattoos, no piercings and no girlfriend, that he sings to Johnny Cash in the car and has a weakness for ice cream, Doyle reveals a nice line in self-mockery by describing his best feature as “my unbelievably muscular body”.

Lavelle is still pondering the next step for Crack Away Jack but Doyle will keep the ride, having stepped into the vacancy left by the retirement of the luckless Barry Fenton. “It's the first time we've started a season with such a high-profile horse and it does feel different,” Lavelle said. “There was pressure on me and on Jack.”

Ironically, the horse to chase

Crack Away Jack home was Squadron, whose trainer, Alan King, is not only Doyle's employer but the handler of the champion hurdler, Katchit. King left without a winner on Saturday but he was sufficiently encouraged to confirm plans for his own stars.

“They all ran well without winning and that tells me they're pretty fit,” he said. “Katchit will go to Kempton next Sunday, so long as the ground is OK, and Voy Por Ustedes will run in the Old Roan at Aintree the following week.”

King is widely thought likely to be the next champion jumps trainer but the dethroning of Nicholls will not come easy. Having mopped up 32 summer races before the end of August, Nicholls had reined in and gone 52 days without a winner, while contentedly telling everyone he would start in earnest on October 11.

He duly won with five of his 11 runners on Saturday, including a four-timer partnered by Ruby Walsh at Chepstow. Walsh's three further winners at Limerick yesterday included Dear Villez, dispatched by Nicholls to win almost €75,000 (about £59,000) in the Munster National.

As he has already plundered the Galway Plate, and has many more forays in mind for his leading chasers, Nicholls is now quoted at only 11-4 by William Hill to be champion trainer in Ireland this winter. The man himself was not present for his latest big-race win - he had agreed to be a celebrity judge at the climax of the Horse of the Year Show.