A combination of factors, including age, anatomy and racing pedigree, are evaluated as owners seek a stake in the next Secretariat, Citation or American Pharoah -- Triple Crown winners of world renown.
As Britain's richest horse race, the Epsom Derby
is particularly influential within the blood stock world.
"It's the source of all derbies," says Dermot Farrington, a prominent agent with decades of experience in the international racing industry. "Every derby after this one is secondary, you have to say."
Epsom racegoers have borne witness to a number of great stallions win on Derby Day over the years, from Shirley Heights in 1978 to Galileo in 2001.
Farrington concedes most will probably win a couple of races"to prove their class" — as See the Stars did in the 2,000 Guineas in 2009.
But few races give a better indication of a great sire in waiting.
"Galileo's become an absolute out-and-out champion sire so I suppose it's history," says Farrington.
Just as a single roll in the hay
with triple crown winner American Pharoah can cost $200,000, significant value is added to a horse when it retires after a Derby win.
"It's a pretty strong test," says Farrington. "You can be sure these horses are tough individuals!"
Watch the video above to find out more.