The rule could not be simpler.
Racing is littered with tales of woe of the horse that could have been anything, the one that had Champion Hurdle, Gold Cup and Grand National written all over it.
Very few reach those great heights, as few reach the level their expectant connections set upon them.
As of yesterday afternoon, however, Don Cossack is no longer one of those horses. He, like his trainer, Gordon Elliott, is an exception.
A striking individual, the imposing son of Sholokov made a bright start to his career, winning three bumpers before embarking on a hurdling career.
At that stage his precocious trainer foresaw big things for the unfurnished five-year-old. His only mistake? To broadcast that to the world.
There have been hiccups along the road – not too many – but in a hot renewal of national hunt’s blue riband, Don Cossack delivered on every ambition his handler ever held for him.
Heavily backed in the ante-post market and through yesterday morning and afternoon, he was sent off the 9-4 favourite to give his trainer and rider, Bryan Cooper, a coveted first success in the race and his owner, Gigginstown House Stud, a second, following War Of Attrition’s victory in 2006.
Don Cossack is a horse which likes room in which to manoeuvre and, when crowded approaching an early fence, Cooper eased him back and ensured thereafter there was never a fear of crowding.
The imposing nine-year-old appreciated the move, jumped very well thereafter, even when getting in close at one fence.
As the race unfolded he, last year’s runner-up Djakadam and King George winner Cue Card came to the fore.
The three approached the third-last travelling well within themselves, and were moving clear of the remainder when, at the obstacle, Cue Card took a nasty tumble.
Immediately it became a battle of the Irish, a duel between our two leading horses and two of our leading trainers, Willie Mullins and Gordon Elliott.
Djakadam has jumped the better of the two but Don Cossack consistently recovered lost ground using his impressively long stride, and as the two turned for home he and Cooper began to assert.
The well-backed favourite stretched clear between the last two fences and, under a strong drive from his rider, galloped home four and a half lengths clear of Djakadam, who had to settle for the runner-up spot for the second consecutive year, with his never-dangerous stable companion, Don Poli, ten lengths back in third, and Carlingford Lough getting up on the line to ensure an Irish-trained 1-2-3-4.
“I can’t believe it, it’s unbelievable. To be honest, I need to look at the race again - I was so nervous all the way around,” said the emotional winning trainer, Elliott.
“It means so much to me to win a Gold Cup - it was something special.
“I’m just so happy for all of us - all the staff in the yard, and my mother and father.
"I’m in a great position - I’ve got a lot of good owners at the moment.
“I can’t thank Michael (O’Leary) and Anita and Eddie and Wendy enough, and all at Gigginstown - they supported me from the start.”
Winning jockey Cooper, who has had more than his share of ups and downs since taking the role as retained rider to Gigginstown, repaid connections’ faith with a fine ride.
He admitted he could scarcely believe how smoothly, and quickly, it went.
“It was over so quick,” said the Kerry native.
“I couldn’t believe I was going that easy turning for home. He went to go round again at the bend after the last, but galloped all the way to the line.
"He jumped great - he only missed one fence all the way round. Other than that, he was foot-perfect.
“Fair play to Gordon and the team, Michael and Eddie - they always believed in him and trained him for this race.”
Cooper listened to numerous calls for him to be replaced aboard the gelding but feels he and connections were vindicated with this victory: “We’ve put all the doubters away now - they all said he wasn’t good enough.
"All the people who said I didn’t get on with him - we’ve put them in their place today.
“There’s only one day - and this was it. He didn’t need cheek-pieces on this ground. He might have needed them if it was soft, but not on that ground.
"We’ve not quite had one good enough this week but this one certainly was.”
The normally pragmatic Michael O’Leary admitted to being overcome by the whole occasion.
“I am actually so emotional, we have been doing seconds all week,” he said.
Bryan gave Don Cossack a peach of a ride and for Don Poli to finish third is brilliant.
“It’s very tough to find those horses. We’ve had a few like Weapon’s Amnesty, who won an RSA Chase and got injured.
"Gold Cup winners are impossible to find. I’ve bought a lot of horses in the past 10 years.
“I am delighted for Gordon. He has obviously had a tough week losing No More Heroes and it was also tough for Bryan.
"To win a Gold Cup is beyond dreams. It is 10 years since we won it with War Of Attrition and what a way to celebrate the anniversary.
“Gordon’s a magnificent trainer, Bryan’s a magnificent jockey. To win a Gold Cup at just 23, ... Ruby [Walsh] has had a great week, but Ruby is the master of riding round here and hopefully Bryan will be the next Ruby.
“What a race it was. Djakadam put it up to him the whole way around and I feel sorry for Cue Card. It is a pity.
"Gold Cups are incredibly hard to win. I’m thrilled. I’m so happy I could cry.”
On what has been a record-equalling week for Irish raiders, with 14 victories in 28 races, O’Leary added: “It’s swings and roundabouts. For a number of years here the Irish had no runners at the Gold Cup.
“Now we have some strength but it will flow back the other side of the channel again. It always does. It’s what makes it interesting.
"For everybody in Ireland, a winner in Cheltenham makes the week and a Gold Cup makes the decade.”
Of runner-up Djakadam, Willie Mullins accepted defeat magnanimously.
“We have no excuses - he had every chance from the fifth-last and jumped as cleanly as he could,” said the Festival’s top trainer.