Acid test for ageless Casey and brilliant Flemenstar

Feisty trainer's talented chaser is the horse of a lifetime – and favourite for the Powers Gold Cup

When he grins, the shrewd stockman's eyes disappear in folds and fissures of flesh, eddying years of weather and worry and laughter. How many years? "I'm 75," Peter Casey says. "Or is it 77? I'm 50 years married, anyway. It was Easter then, as well – and I had the Irish National winner backed. I was going off on my honeymoon, down the west or somewhere, and listened to the race in my car."

You can only hope his wedding speech was not as candid as his notorious television interview at Leopardstown in January. Casey had just watched the best horse he has ever trained, and perhaps the best young jumper in all Ireland, win a Grade One novice chase by 19 lengths. "I can't believe it," he told Tracey Piggott, live on RTE. "I'm going to have feckin sex tonight and everything."

At 6.15 the next morning, a nephew rang from Thailand. The lascivious sensation – propelled by "Facetube and I don't know what" – had already rippled across the world. Shortly afterwards came the first call from a radio station. "Junie's right here beside me," he told them. "Here." His long-suffering wife chatted politely, unaware she was on air. At breakfast, a man came in carrying the post. He was from a tabloid. An RTE chat show, The Saturday Night Show, put them up in a big hotel in town. "A suite!" The eyes sink from view again.

Fifty Easters on, Junie knows to expect the unexpected. But neither ever imagined they might end up with a champion like Flemenstar. In Stamullen, just up the coast from Dublin, it is a wild, perishing afternoon, but the horse looms out of the shadows of his stable in shimmering, shifting slabs. He is a mastodon and, only seven, Cheltenham had to wait a year. On Sunday he faces his biggest test yet, at Fairyhouse, in the Powers Gold Cup. "If he wins, he'll be [Cheltenham] Gold Cup favourite," Casey says. "We're like Tom Foley, when he had Danoli. We've come up with one good one in our lifetime."

They came home from their honeymoon to the Casey farmstead: The Palace, an address of sumptuous irony. They were given a thatched cottage with no electricity. He had pursued Junie implacably. "I used to see her coming to Mass, I'd be standing outside watching," he recalls. "Jesus, I thought, that one has a grand pair of legs. And I'd go in after her."

Junie was nine years his junior, barely 16. "Can we not go to another Mass?" she implored her family. "That Casey lad will be whistling at me." Finally she agreed to go to the pictures; at 18, she agreed to marry him.

That first dwelling is now a tack-room, with the bridles and girths needed for perhaps 30 horses, including the mares, foals and sundry animals that need to be sold on. The dam of Synchronised, the Gold Cup winner, came through here once. But Flemenstar is one of just 14 in training. "I wouldn't know how many horses are here," Casey says. "I daren't count them. Too many of them are mine, and I don't know how I'm going to stick it."

Flemenstar does have an owner, who sent him here, albeit the horse has since been nearly sold several times and the offers are getting bigger all the time. For now he represents the unreckoned fulfilment of a knack that long lay cold after Casey's boyhood dreams were ended. "I wanted to go off to be a jockey but I was an only son and my father wouldn't let me," he says. "You'd be sent off to work in the fields and there'd be another lad with me and we'd race these working horses bareback just with the winkers, no bridle or anything. I rode one point-to-point, that was it."

Instead Casey became a ploughman and sheep-shearer, a pound per fleece. "I won a heap of prizes in a Ferguson tractor, when only a lad of 16," he says. "And I'd shear a hundred a day, taking me time. I could have done 200 no trouble, but couldn't take that money off a farmer in the evening. Then I'd say: 'Damn them sheep, I'm going to the races'. And lose a heap of money. I was a hoor for backing horses."

Apart from draughts, however, he never meant to have any on the farm. He gestures at Junie. "Only for her breeding the three chaps, we would never have had anything to do with them," he says. "But these lads came along and started off pony racing. And we bought a couple, bred a couple, started to train a few."

That so aimless a journey could lead to such a destination will again cause his mind to wander at Easter Mass. "Before Leopardstown I never slept all night," he says. "And I went to Mass and never said one prayer, I was thinking and thinking the whole time on the horse, what can go wrong. So I know I won't sleep Saturday night. And if he wins, I won't sleep on Sunday night either – and you know why that is." Junie rolls her eyes.

"But I never thought I'd live to see a horse like this," her husband says. "Though I never thought I'd live to see Dublin win another All-Ireland final, either. And b'Jesus they did last year. I watched them the other day, mind, and know I won't see them do it again."

Nor will there be another Flemenstar, but the privilege is not wasted on Casey. "Sure, I should be retired," he says. "Thirteen years ago, Christmas Eve, I'd been away dancing. I was a hoor dancer, Jesus, I would dance all night. And I came back and didn't feel right and I needed a treble bypass. Then I had a new hip, seven years ago, and the lungs are gone about five. And I had three stents in just before Christmas. I'm only a quarter what I was."

In which case, what chance did the teenage Junie ever have? "I'm a rare one." Casey gives another delighted laugh, only this time the eyes stay fixed. "Am I? Huh? What do you think? D'ye think I'm rare? Do yer? Huh? You won't meet many like me."