With horse racing in Ireland dating back to at least 60 AD, it is easy to see why the sport is so deeply entrenched in our culture. And perhaps having horse racing in the blood is why we can claim to have produced some of the greatest race horses in the world. It would be interesting to know the form of the horses that took part in races of ancient times and how they would compare to their modern-day counterparts. But as that is not possible, here is a look at the five greatest Irish-bred racehorses of all time. Well, since records began.