For many years after World War II the breeding pundits used to tell us that a colt with pretensions to Derby success should have a sire and a broodmare sire who had both shown top-class form over a mile and a half. That was all well and fine, but generally not terribly helpful to punters, as most of the runners tended to fit that description; breeders seeking to produce a foal capable of Derby-calibre performance naturally operated on those lines, and they were not short of options, stayers being prevalent among the stallion population.

Anyone aware of what passed for a rule in those days would have shied away from Ki Ming in 1951; how could a son of Ballyogan (whose five successes had all been over five furlongs) start favourite at Epsom? The very idea! That was a little before my time, and just when it was that I became conversant with the theory I don’t recall, but it must have been after 1958, or I would not have been able to convince myself – as I did – that Hard Ridden was going to win.

Hard Ridden was by Hard Sauce, winner of a July Cup and second in a King’s Stand, and he stood out as the sole exception to the rule until American pedigrees came to the fore in the late 1960s. Sir Ivor was not just another exception; he ushered in a new era when no plausible formula existed. Mill Reef was by a horse – Never Bend – who was beaten every time he ran beyond nine furlongs; Roberto’s sire Hail To Reason began in races over three furlongs and broke down irreparably as a September two-year-old, having just won over seven, the longest distance he ever attempted.

I’m inclined to believe that this year’s Derby hero has a pedigree quite unlike that of any of his predecessors

I well remember informing my Sporting Life readers on Derby Day 1977 that Blushing Groom could not win, basing my opinion not so much on the fact that his sire Red God had been a sprinter, but on my extensive research that showed that in a lengthy innings at stud Red God had never sired any kind of winner at 12 furlongs. I might have congratulated myself over rejecting the 9-4 favourite, if he had not finished an honourable third, well in front of the stumer I recommended.

We have now long since become accustomed to Derby winners whose sires had no form at a mile and a half, most notably, perhaps, Dr Devious and North Light, sons respectively of Ahonoora and Danehill. Their victories came as no surprise, both starting at single-figure odds, trusted to stay by reason of potent stamina influences on the distaff side of their pedigrees. We have even had a Derby winner – Oath – whose sire (Fairy King) finished last on his only racecourse appearance. These days, anything goes, it seems.

Even so, I’m inclined to believe that this year’s Derby hero – who preserved his unbeaten record with a brilliant display in the Eclipse Stakes – has a pedigree quite unlike that of any of his predecessors. Check out his seven closest male ancestors – sire, two grandsires and four great-grandsires, and it is easy to understand why his owner and breeder, Anthony Oppenheimer, failed to make him eligible for Epsom until his impressive performance in York’s Dante Stakes convinced him to stump up the £75,000 supplementary fee.

Golden Horn is by Cape Cross, who was in training for four seasons, winning five of 19 starts. His one success at the top level came in the Lockinge Stakes at four, when he ran as a presumed pacemaker and caused a 20-1 shock.  Third and fourth in two other Group 1 events, the Prix Jacques le Marois and the Queen Elizabeth II Stakes that season, he added Group 2 wins in the Queen Anne Stakes and Celebration Mile as a five-year-old. As the record shows, incontrovertibly, he was a miler.

Cape Cross is by Green Desert, who raced only at two and three, winning five of 14 races. His victories came in the Group 3 July Stakes and Group 2 Flying Childers Stakes as a juvenile, and in the Free Handicap, the Group 1 July Cup and Group 2 Haydock Sprint Cup in his second season. He tried a mile three times, notably when finishing second in Dancing Brave’s 2,000 Guineas, but he did not win beyond seven furlongs and proved most effective as a sprinter.

Golden Horn’s dam Fleche d’Or is a daughter of Dubai Destination, who was in training for three seasons, winning four of eight starts. His successes at two both came at seven furlongs, more importantly in the Group 2 Champagne Stakes, but at three was seen out only once, as runner-up in Listed company at Goodwood over 11 furlongs. At four he was kept to a mile, winning twice, including the Group 1 Queen Anne Stakes, from four efforts; he was retired after poor shows in the Prix Jacques le Marois and Queen Elizabeth II Stakes. He could cope with further, but it was as a miler that he made his reputation.

Green Desert’s sire was Danzig, who performed sensationally in training with Woody Stephens, and may well have been the fastest of all Northern Dancer’s sons. But he was never wholly sound. He won a maiden at Belmont Park over five and a half furlongs on his debut at two, and at three he won allowance races at Aqueduct over six furlongs and Belmont over seven. That was it – three wins from as many starts, never tested at stakes level. He could only be classified as a sprinter.

Cape Cross’s dam, the admirable Park Appeal, was by Ahonoora, who won seven of his 20 races in a three-season career. As a juvenile he won a six-furlong maiden at Newbury and was twice placed second from three starts. He scored twice from nine runs at three, taking the Stewards’ Cup at Goodwood (receiving 19lb from the top-class sprinter Double Form) and a five-furlong handicap at Newbury under top weight of 10st. He graduated in Pattern company as a four-year-old, when he took the Group 3 King George Stakes at Goodwood and profited from the disqualification of Thatching in the Group 2 Nunthorpe Stakes, both those wins coming over five furlongs. Self-evidently, he was a sprinter.

Dubai Destination’s sire was Kingmambo, a son of Mr Prospector who was trained in France. He won only a six-furlong maiden from seven starts as a two-year-old, though was three times second in Pattern company, and at three won four out of six – the Listed Prix Djebel at seven furlongs, the Poule d’Essai des Poulains, the St James’s Palace Stakes and the Prix du Moulin de Longchamp, all at a mile. He never ventured beyond that trip and was decidedly a miler.

Fleche d’Or’s dam Nuryana was by Nureyev, whose career was limited to three starts. A rare Pattern winner on debut, in the Group 3 Prix Thomas Bryon over seven furlongs, he returned the following spring for a victory in the Listed Prix Djebel over the same trip. Then came his fateful visit to Newmarket for the 2,000 Guineas, when he looked much the best but was disqualified for having caused interference. He was favourite for the Derby when he took sick, and he missed that and every other engagement. The limit of his stamina was anybody’s guess, but on his public form he had to be considered a miler.

Was there ever, before Golden Horn, a Derby winner whose male ancestors in his closest three generations were all sprinters and/or milers and never so much as managed a single start over a mile and a half? I fancy he is unique in that regard – and, incidentally, one of the best Derby winners of recent years.

I am reminded of the wise words penned by that great writer Joe Estes many years ago: “Pedigrees are useful only when we are ignorant of the merit of the individual, and not very useful then. The more we know about the individual and its progeny the less we need to know about the pedigree. When we have a moderately complete record of the individual and its progeny, the pedigree becomes useless.”

In light of the evidence supplied by Ouija Board and Sea The Stars, why would we imagine that Cape Cross would inhibit Golden Horn at a mile and a half?