O'Brien aims to take final step with his second crack at National service

Irish nephew of Aidan O'Brien came agonisingly close last year but can go one better this time

In the weighing room, one of the harshest courtrooms of them all, in which horsemanship and character are swiftly assessed, it does not take long for the jury to differentiate between the pretender and the real McCoy. Or should that be the next McCoy? Wednesday, at Kempton Park, and the jockeys' valet Shane Clarke, a man who prepares the real Tony McCoy – among others – for the rigours of jump racing, speaks for many. "Tom O'Brien will be the next champion," is his confident verdict on the young Irishman just going out to ride his first of the afternoon. "It's a certainty. He's a quiet lad but very well thought of by the senior lads – very highly rated."

Few doubt that O'Brien, who in 2004 left Ballydoyle, home to the fabulous Flat horses trained by his prodigiously gifteduncle Aidan O'Brien, and headed across the Irish Sea, will ultimately succeed his compatriot and 12-times champion. Last seasonthat was a given after a record of 105 winners from 556 mounts.

This season it has been tougher, as he has entered a transitional period after losing his conditional claim (the weight allowance for less experienced riders) and thus far has amassed 62 victories from 517 rides. "I knew it would not be easy to live up to last year, and it's been hard," he says. "But I'll keep going." He adds, with a smile: "I've had a lot of seconds, mind [69]. A few too many. So you could say I've been unlucky." As many said of him after last year's John Smith's Grand National.

A year on, the 21-year-old is entitled to believe, if there is any justice, that he will prevail on Peter Bowen's charge McKelvey. Last year, given his first ride in the Aintree showpiece, or nine minutes of mayhem, depending on your perspective, the partnership was maddeningly close to victory. Three-quarters of a length; that's all the difference there was between O'Brien's mount, as he galvanised everything from the horse, and the winner, Silver Birch, at the line – and then it was discovered that his horse had injured a tendon.

The Haverfordwest-based Bowen maintains that, had it not been for this misfortune, his charge would have yielded the first Welsh-trained winner of the National in over a century. O'Brien concurs: "It was very disappointing. I only realised the horse was lame when he pulled up at the end of the race. Apart from that I'd have had a good chance."

Though he was initially dejected by the experience, O'Brien swiftly moved on; reminiscent, in a way, of F1's Lewis Hamilton after capitulating in the final furlong of his own season in Brazil. McKelvey had preceded last year's National with victory in a hurdle race at Bangor. This time, things do not appear so propitious. But Bowen insists: "McKelvey has had two quiet runs, and finished lastat Newcastle last time, but I wouldn't worry about that. He's spot-on. I'm happy with him."

O'Brien places his trust in the trainer. And the Lord. "Please God, if the game's good to us, we'll get plenty of goes at the National," he says. "Hopefully I'll come across a horse good enough some day – and hopefully it will be this year. If I've got the same horse I had last year, I'll do it – but I won't know that until the day." The Co Wexford-raised rider nominates the ante-post favourite, Cloudy Lane, trained by Donald McCain Jnr, son of Ginger, who won three Grand Nationals with Red Rum and another with Amberleigh House, as his principal rival. "The way he's been running, and with connections who've proved they can do it he looks like the one," says O'Brien.

For some participants, the mental obstacles can prove as hazardous as the constructions of birch over the four-and-a-half-mile course. Yet when you broach the perils of misjudgements and simply the fear of riding into the unknown, he retorts, almost with disdain: "The fences are bigger and there are loads of runners. Other than that, it's just another race at the end of the day." In no sense is he being arrogant. It is more a refusal to be overawed by an event that, more than any other race, captures the nation's imagination, and many of its pounds.

It was almost inevitable that this would become his life in view of the influence of Aidan O'Brien, who prospered as a jumps trainer in Ireland before turning to the Flat 13 years ago, and Tom's father, Jim, assistant to the master of Ballydoyle.

"I used to ride out horses like [Derby winner] High Chaparral and Rock Of Gibraltar [the miler who won seven consecutive Group One races] for Aidan when I was younger and I always wanted to race-ride, but I got too heavy for the Flat. So this was was the obvious choice."

O'Brien joined Philip Hobbs's powerful yard in Minehead, Somerset, initially as an amateur rider. Now Hobbs has first call on him, although O'Brien rides many winners for Bowen. "With his background at Ballydoyle, and having Aidan as his uncle, that's been a major asset," says Hobbs. "He's been involved with top-class Flat horses from a young age. His father and Aidan are very good influences onhim. Their input has been very helpful to his career."

"He's progressed again from last season but, even though he's a very talented jockey, to really get on he needs a number one job in a top yard," adds Hobbs. "I'd have every confidence that, long-term, he will achieve that. A future champion? Definitely, yes, if things go right for him." He surely cannot fail, given a touch of O'Brien family magic.

Aintree coverage starts on Saturday on BBC2 at 1pm, moving to BBC1 at 2.30pm. The big race sets off at 4.15pm.