To stand Paul Rooney before a herd of horses is akin to watching a child running riot in a sweet shop.

He is happy to admit it. “When I look at horses all I see is that they have four legs, a head and a tail,” he says. “When they look at me back, they all look as though they love me. I don’t think I have ever seen a horse I don’t like. And if it’s a chestnut with lots of white about it, there’s a good chance I will buy it.”

A very good chance. So much so that Rooney and his wife Clare have advanced from anonymity to owning one of the largest jumping strings in Britain over the last five years. They now have 120 horses in training, spread out among 24 different trainers.

This time last year they had 90 horses, the vast majority with Donald McCain, but following a well-documented split, the Rooneys realigned their interests in a way that leaves them feeling harmonious with their involvement. It was a lesson well learned. The bout of indigestion plaguing the child who looted the sweet shop has passed.

It must have been an uncomfortable time. To read about the schism was to visualise Rooney as the hard-nosed businessman who took his company, the Horsham-based Arun Estates, into the Sunday Times Rich List for the first time last year. To meet him in person is to encounter a profoundly content man, one who has stumbled upon the elixir of racing, and is now profoundly in thrall.

Racing has taken over Paul’s life. We left Sussex and came up here to get away from all the people who wanted a piece of him. We wanted to slow down. But that hasn’t happened

Danny Zuko, inevitably a chestnut, started it all. “I paid four grand for one-third of him and he won a couple of races,” Rooney recalls with a broad smile. “We brought him home when he retired [in 2011], and I said to Donald [McCain] that if something came up, we’d be interested in taking a whole horse for ourselves. And the phone never stopped ringing.”

Today, Danny Zuko looks rather pleased with himself. He is one of half a dozen Rooney-owned horses enjoying retirement at the couple’s property in the Scottish borders. Every stable door has a brass plaque, but the name etched onto the plaques is the horse’s nickname, rather than his racing name.

Now 13, Danny Zuko and his fellow-cohorts attest to the fact that the Rooneys’ love of horses runs more than skin deep. A new stable block was built to accommodate them; another is going up soon to cater for others that will follow.

This equine retirement home is really Clare’s territory. Paul, 68, looks on with the air of a benevolent grandfather while Clare darts about attending to the horses’ every whim. It doesn’t take long to recognise people well versed in horses, and it’s no surprise to learn Clare was a keen dressage rider.

Also in attendance is Jason Maguire, the jump jockey sidelined by a long-term injury from which he will do well to return to the saddle. During his enforced absence Maguire has become the Rooneys’ confidante. He has steered the couple onto a platform from which they can now do what they always aspired to when they got into the game. All they ever wanted was to enjoy it.

Both were newcomers to racing. Paul watched the Grand National on television every year and had made a few social visits to the races. “Horses were new to me,” he says. “I once went riding with Clare and my horse ran away with me. I’m not the most balanced, so I said: ‘never again’. But it was Clare’s love of horses that got us into it.”

So why racing, rather than dressage, in which Clare was already proficient? “I had a pretty good idea Paul wouldn’t be into dressage,” Clare says. “There is not enough action for him. Racing excited Paul and we wanted something we could do together.”

Paul’s passion has since became all-consuming. “It has taken over his life,” Clare says. “Ten years ago we made an agreement. We left Sussex and came up here to get Paul away from all the people who wanted a piece of him. We wanted to get away from the traffic, and slow down. But that hasn’t happened.”

Like so many before him, Paul found his early successes intoxicating. He started the 2011 season with three horses, each of which won first time out. “The thrill of winning kicked it all off,” he reflects.

I never envisaged having so many in training. When we got up to ten, Clare said we should stop. I agreed, but I didn’t say at which multiple of ten. So it went on and on

Now hooked, Rooney wanted more. In the three subsequent seasons his string swelled to ten, to 35 thereafter, and to 90 beyond that. “I never envisaged having so many in training when we first started,” he says. “When we got up to ten, Clare said we should stop. I agreed, but I didn’t say at which multiple of ten. So it went on and on.

“We went head over heels into it,” he continues. “We bought some very expensive ones, too, but now we are going to tread water. We have a fairly young string with 15 new stores coming through at the moment. We feel we have some bought some good stock, so this is a very exciting time for us.”

As Rooney speaks, it’s tempting to believe he might not have bought so many but for the promptings of others. But that would be to underestimate his passion. When asked if he would do the same if he was starting from scratch tomorrow, he smiles as he lets the question percolate through him.

“I think I would be exactly where I am now,” he replies. “The buzz you get from horse racing is amazing.”

Indeed, a recent development has seen the Rooneys diversify into breeding horses for the Flat. Although Paul’s heart is with the jumpers, Clare finds it stressful watching them leave the ground. “Even if we know our horse has won and are watching a replay, Clare still gets nervous watching the horse and jockey jumping fences,” Paul says.

Kruzhlinin will represent the Rooneys in this year’s Grand National

Her nerves will thus be frayed on April 9, when two horses are likely to represent the couple in the Grand National. Both The Last Samuri, trained by Kim Bailey, and Kruzhlinin, from Philip Hobbs’s stable, are among the leading fancies for a race in which Kruzhlinin finished a respectable tenth in 2014.

It’s fair to say Paul will approach the occasion with greater relish. “I’ll get a big kick from watching it,” he says. “Last time we saw Kruzhlinin in the paddock but it was a bit of a nightmare trying to find a place to watch the race. Clare and I got separated, so we have taken a box this year. I’ll have Clare’s hand squeezing mine during the race, when I’ll be jumping up and down and throwing out a few expletives.”

Beyond Aintree, the couple are keenly anticipating a Flat season in which they will campaign around 15 horses. Most are with Clive Cox, who excelled for them last year. My Dream Boat gave Rooney his greatest thrill in racing to date when he won a handicap at York’s Ebor meeting in August. The four-year-old subsequently won a Group 3 race in France.

But the real kick from their involvement in Flat racing stems from breeding their own. Their first foal, by Showcasing out of the well-related Sadler’s Wells mare Costa Brava, was born last year, when they were also active in the yearling market. They have since added three more broodmares to their portfolio.

“Your interest in horse racing keeps developing,” Rooney says. “It keeps moving, keeps taking you in different directions. For me, it’s nice to have a balance.”

Despite his earlier assertion, Rooney does not seem as though he is treading water when it comes to buying horses. He says that further broodmare purchases are likely to follow, and when he went to a store horse sale with Maguire recently, two horses interested them – yet they came home with 12.

“What can you do?” he asks, once again with a broad smile. “I’m a competitive person by nature, I can’t just take the laid-back approach. I’ll admit I have been a bit surprised by how expensive it is to have horses, but that’s almost a given, isn’t it?

“Horse racing just pulls you in,” he continues, “and racing is a very social scene. Sure, it can be frightening when you add it up. We’ve spent around five million, but we thoroughly enjoy it and we’re very lucky to be able to do it. Years ago I was working flat out. I had no time for hobbies, but I do now.”

So there you have it. At every turn, in every circumstance, Rooney is bowled over by the majesty of animals that generate frisson within him whenever they compete. And competition is certainly the watchword. As with so many self-made men, Rooney wants to win.

Three or four years ago someone asked me what I wanted from racing and I replied I wanted a Grand National winner, a Gold Cup winner and a Derby winner. Why not?

“Winning is everything,” he says. “I want to be involved in the big races. Three or four years ago someone asked me what I wanted from racing and I replied I wanted a Grand National winner, a Gold Cup winner and a Derby winner. Why not? I know that to win just one of those would be amazing, but if you’re in this game you’ve got to dream. My dream is to have top horses.”

Then follows a curious twist. Although winning means so much, which is hardly surprising for a man whose professional advance in the property sector has been matched by few others, one thing means more still. It all goes back to those retired racehorses at home, who live like kings.

“We think of ourselves as considerate owners,” Rooney says. “We’d never push; we don’t want any of our horses to get injured. The instructions to our jockeys before any race are always the same: get yourself and the horse round safely.

“Yes we want winners, but not at any cost. Clare hates it when our horses fall, which is why she is now keener on the Flat. We have lost a couple on the racecourse, which was really hard because you always find yourself asking why.

“But I do believe they enjoy the job. We’ve seen that for ourselves; some of them decide they have had enough. It’s like humans – none of us feels like it every day of the week. And when they have had enough, we will bring them home.”

An operation in transition

Largesse brings with it some unexpected difficulties, and for Paul and Clare Rooney, the decision to move their 70-strong string from Donald McCain’s stables in October generated unwelcome headlines.

Having outlined his reasons at length at the time, Paul Rooney is reluctant to discuss it further. The McCain yard was plagued by a virus and the vast majority of Rooney’s horses, which McCain had bought for him, were caught up in it. Rooney decided to spread his horses among a broad raft of trainers to avoid a repeat scenario.

Asked whether he understood the implications for any trainer who lost so many horses all at once, Rooney replies: “That wasn’t the way I wanted it to happen.” He wouldn’t elaborate, although it later emerges his original plan was for McCain to keep 30 horses. As relations became strained, however, that plan dissolved.

It’s not the sort of chapter welcomed by anyone whose motive for getting involved was to enjoy it. Indeed, the last five years have been a steep learning curve for the Rooneys, particularly in establishing who they could trust. There even came a point when Paul wondered whether he had done the right thing, although such thoughts are now distant.

“Until this season we had too many horses with one trainer,” he reflects. “We won’t make that mistake again. We have 24 trainers now and none has more than seven or eight horses. And with Jason [Maguire] alongside us, we run things a lot more professionally.

“We’re much more in tune with things on our side,” he continues, “and that makes me feel very comfortable about what’s going on. This is a transition season for us but we’re still doing well. It should pick up again next year, when I’m sure we will have some really exciting times.”