But very occasionally, a trainer comes along that defies all conventions, progressing with almost impossible speed, raising the bar as they go and pushing the boundaries of what previously seemed possible. This is the story of Aidan O’Brien.

50 years to the day after Vincent O’Brien had first taken out a licence to train racehorses, the Master of Ballydoyle retired from the profession he had made his own.

A 13-time Champion Flat Trainer in Ireland, he had trained six winners of the Derby at Epsom, three winners of the Aintree Grand National and countless other big-race winners around the racing world.

Not only that, he had been such an innovator and was so influential that he would later be voted the greatest figure in the history of horse racing. In terms of shoes to fill, they don’t get much bigger than those.

At the time Vincent retired, Aidan, who is no relation, had only just turned 25. In the context of world-class Flat trainers, this is an impossibly young age. However, evidence had already been mounting that this was no ordinary young man.

With Aidan O’Brien having married Annemarie Crowley, daughter of trainer Joe Crowley, the young couple oversaw phenomenal expansion of their yard on Owning Hill.

This saw them quickly claim the title of Champion National Hunt Trainer in Ireland, first under Annemarie’s name in 1992/3 (the same season that Aidan was crowned Champion Amateur Jockey in Ireland), then in Aidan’s name for the five years that followed.

In Aidan’s first full year with a trainer’s license in 1994, they smashed the record for the number of winners trained in a calendar year in Ireland with a tally of 176 primarily National Hunt winners. The following year, they saddled a scarcely-believable 241 winners.

With John Magnier and Coolmore being on the search for the best candidate to attempt to fill the substantial void left by Vincent O’Brien in Ballydoyle, Aidan and Annemarie’s rapid surge to the top of the National Hunt ladder couldn’t have been better timed.

Indeed, the first public hint of what lay ahead came just weeks before Vincent announced his retirement when Aidan signed for a yearling filly by Sadler’s Wells that cost IR£275,000 at Goffs and was rumoured to have been bought on behalf of Coolmore.

Sure enough, it wasn’t long before it was confirmed that Aidan and Annemarie were to move their Flat horses to Ballydoyle and train a string of horses for John Magnier’s Coolmore operation there.

This began what must have been the most manic of times for the O’Brien’s. The public and private pressure of taking over the running of Ballydoyle from the greatest trainer that had ever lived must have been enormous.

It had also been just over a decade since an older, even more decorated National Hunt trainer in Michael Dickinson had failed to transfer his talents to Flat racing after being moved to the no-expense-spared Manton Estate under the patronage of Robert Sangster.

If Dickinson couldn’t even come close to making such a transition, what chance would these young upstarts have?

As if the pressure and sky-high expectations weren’t enough, the circumstances at the time dictated that Aidan wasn’t in a position to concentrate solely on Ballydoyle. For three years he was splitting his time between Ballydoyle and Owning Hill, speeding between the two yards that were 45 kilometres apart every day to oversee two huge strings of horses under both codes.

And if all that wasn’t enough, Aidan and Annemarie’s first child Joseph arrived in May 1993. In the five years that followed he was joined by Sarah, Ana and Donnacha.

It is difficult to imagine just how hectic and high-pressured the professional and personal lives of the O’Brien’s must have been at the time. However, if they were feeling any pressure, it certainly wasn’t reflected in the performance of their horses on the track.

In those transitional years, many of the O’Brien highlights continued to come under National Hunt rules, with him training Istabraq to become a legend of Irish racing by winning the Champion Hurdle at the Cheltenham Festival on three occasions and 11 other Grade 1 races.

However, the wheels were very much turning in Ballydoyle too. The final Group 1 win of Vincent O’Brien’s training career was Fatherland in the National Stakes at the Curragh in 1992. Thus, there was a wonderful symmetry in the four-year absence of Group 1 victories in Ballydoyle being ended by Aidan saddling the first Group 1 winner of his young career in that very race with Desert King four years later in 1996.

The following May, O’Brien secured his first Classic wins when sending out Classic Park to win the Irish 1,000 Guineas (also saddling the runner-up) and Desert King to win the Irish 2,000 Guineas on the same weekend. Desert King went on to win the Irish Derby a month later.

Just in case anyone was under an illusion that such success was fleeting, O’Brien saddled three individual Group 1-winning two-year-olds at the backend of the 1997 season. It was clear that the fortunes of Ballydoyle and the O’Brien family were only going in one direction.

O’Brien would go on to be crowned Champion Flat Trainer in Ireland for the first time in 1997. Given that he was also crowned Champion National Hunt Trainer in 1996/7 and 1997/8, this was the first time in modern history (post-1950) that a trainer had been crowned Champion Trainer on the Flat and over jumps in the same year in Ireland. One suspects that is a feat that will never be repeated.

It wasn't until the beginning of the 1998/9 National Hunt season that O’Brien ceased to commute between Ballydoyle and Owning Hill. His sister-in-law Frances Crowley took over the licence in Owning and O’Brien would only continue to train a handful of National Hunt horses at Ballydoyle, most notably the legendary Istabraq.

The emphasis with the O’Brien’s was now firmly on Flat racing and 1998 saw him gain his first Classic wins in Britain, with King Of Kings winning the 2000 Guineas at Newmarket and Shahtoush winning the Oaks at Epsom.

The reduction in horse numbers brought about by the relinquishing of Owning Hill led to O’Brien losing his Champion Flat Trainer title to Dermot Weld in 1998, but the wheels were still a long way from hitting top speed at Ballydoyle.

It is a remarkable fact that Vincent O’Brien enjoyed all the success that he did at Ballydoyle whilst seldom having more than 50 horses in his care. In the years that followed Aidan’s move to Rosegreen, the yard would steadily expand to house 200 thoroughbreds at all times. This expansion soon started to become evident in rising numbers of winners and 1999 saw O’Brien reclaim his Champion Flat Trainer crown by saddling 102 winners. He hasn’t relinquished it since.

The year 2000 saw O’Brien produce his first international superstar. Giant’s Causeway had won a Group 1 in France as a juvenile, but it was the remarkable winning run he embarked on that summer which saw him truly make his mark.

He won five of the most prestigious Group 1 races on either side of the Irish Sea in the space of just over 10 weeks, becoming known as “The Iron Horse.”

He further endeared himself to the public by routinely displaying a tigerish attitude that had his rivals plotting ways to avoid getting into a duel with him. His remarkable season finished with a tremendously game effort on dirt in the Breeders’ Cup Classic which saw him lose out by just a neck to Tiznow.

Just five years into the job, O’Brien had already secured 54 Group/Grade 1 wins on the Flat up to the conclusion of 2001. It was clear that for the second time in history, something very special was happening in Ballydoyle. Little could anyone have known that the O’Briens and Coolmore had yet to hit top stride.

Just two years on from Giant’s Causeway, O’Brien produced another superstar to go on an incredible run of Group 1 success in Rock Of Gibraltar.

In the space of a year, he won seven consecutive Group 1 races in Ireland, Britain and France. That year also saw him complete a memorable 1-2 in the Derby, with High Chaparral beating Hawk Wing. The Group 1 winners continued to flow in the years that followed.

The enigmatic George Washington had an array of quirks including a refusal to walk through the famous arch in the pre-parade ring at the Curragh that endeared him to many, but O’Brien harnessed his raw talent to win four Group 1s.

Another notable training feat was his handling of Yeats, the great stayer that he brought back year after year to win an incredible four consecutive renewals of the Gold Cup at Royal Ascot.

However, for all the phenomenal success of the O’Brien’s in their first decade in Ballydoyle, a crucial juncture in their fortunes and those of Coolmore was approaching in the mid-noughties.

The great Danehill had died prematurely in 2003 and Sadler’s Wells, one of the greatest stallions to ever live and Coolmore’s flagbearer, was reaching the end of his time as an active sire, eventually being retired from breeding in May 2008. An heir to the throne had yet to become clear at Coolmore and one can be sure that this was causing anxiety in the camp.

Then, as if sensing the urgency of the matter at hand, his son Montjeu burst to prominence as a sire in 2005 when producing Motivator to win the Derby from his first crop.

Montjeu would go on to produce three more Derby winners amongst a parade of stars including the O’Brien-trained Camelot, St Nicholas Abbey and Fame And Glory.

Just a year after Montjeu’s emergence as a world-class sire, lightning struck twice and even more spectacularly for a Coolmore-based son of Sadler’s Wells as Galileo produced Nightime (Irish 1,000 Guineas), Sixties Icon (St Leger) and Red Rocks (Breeders’ Cup Turf) in his first crop. With his second and third crops producing consecutive European Champion Two-Year-Olds in Teofilo and New Approach amongst many others, it was soon clear that Galileo was the new heir apparent.

Aidan O’Brien and the Ballydoyle team soon discovered that sons and daughters of Galileo thrived in Rosegreen just as well as their father had. While O’Brien would have to wait a few years to get his hands on the blue-blooded progeny of Galileo that Coolmore would begin to produce after he had announced his arrival as a tip-top stallion from 2006 onwards, he wasted no time making hay with those that he was sent in the years that immediately followed.

Soldier Of Fortune became the first son of Galileo to win a Group 1 for Ballydoyle in the Irish Derby in 2007 and Rip Van Winkle became the second when winning the Sussex Stakes at Goodwood in 2009.

Though, it wasn’t as if Aidan O’Brien was struggling for firepower as he waited for the conveyer belt of Coolmore-bred offspring of Galileo to reach Ballydoyle, as 2008 saw him match his previous best of 23 Group/Grade 1 wins in a year. The world record for such victories had been taken from him by Bobby Frankel who won 25 Group/Grade 1s in 2003, but O’Brien wouldn’t be finished with that record just yet.

It was in the autumn of 2009 that the first big group of regally-bred yearlings by Galileo arrived in Ballydoyle. This would prove to be the start of a turning point in world racing.

Roderic O’Connor and Misty For Me led the initial charge of the Ballydoyle-Galileo brigade, both winning Group 1 races as juveniles before going on to win the Irish 2,000 Guineas and Irish 1,000 Guineas respectively.

For good measure, Treasure Beach became the third Classic winner from that Ballydoyle crop when winning the Irish Derby.

If there had been any lingering doubts about Galileo’s future as the world’s leading stallion, the emergence of the imperious Frankel in 2010 put that to bed. It couldn’t have been clearer that Galileo was both the present and the future. Coolmore were soon going to every corner of the racing world to buy Group 1 racemares and producers that were considered likely to suit Galileo. The results of this highly-selective and targeted approach would prove to be sensational.

In the meantime, with 10 years having passed since O’Brien had last won the Derby with High Chaparral in 2002, that run of misfortune was about to be replaced with a run of unprecedented success.

With Camelot having brought the drought to an end under Aidan’s 19-year-old son Joseph in 2012 (becoming the first father-and-son trainer-jockey combination to win the Derby in its history spanning over 200 years), O’Brien has won six of the last 10 renewals of the Derby.

Four of those were sons of Galileo, one was by Montjeu and the other was by Montjeu’s son Pour Moi. The 2019 renewal that was won by Anthony Van Dyck was particularly notable for O’Brien, as he was responsible for five of the first six horses home.

The parade of champions that has flowed out of Ballydoyle in the last decade are simply too numerous to do justice to without many more thousands of words. From 2011 to 2020 Aidan O’Brien secured no less than 169 Group/Grade 1 wins around the world.

This relentless stream of excellence culminated in another record-breaking performance in 2017. Having had his previous world record of 23 Group/Grade 1 wins in a year surpassed by Bobby Frankel who won 25 Group/Grade 1s in 2003, O’Brien raised the bar yet again by securing 28 such victories in 2017.

The last decade has also seen the O’Brien’s extend their long list of achievements to that of being highly-successful Group 1 producers themselves.

Ultimately, that has been the consistent theme throughout Aidan O’Brien’s 25 years in Ballydoyle. Bars being raised, standards being lifted and new ground being broken.

This phenomenal operation is likely to face another crucial juncture in their history when the now 23-year-old Galileo’s breeding career comes to an end.

However, with a world-leading broodmare band in Coolmore and a trainer of Aidan O’Brien’s standing and experience at the wheel in Ballydoyle, it is hard to imagine anything but continued world dominance for the O’Brien’s, Ballydoyle and Coolmore in the years ahead.