He won the St. Leger Stakes in 2000, and, unusually for a Classic winner, stayed in training until the age of eight, winning many important races over middle and long distances.
Dropped down to maiden race company for his three-year-old debut, he recorded a first victory at Newbury[4] before moving into Classic contention by winning the Chester Vase.
In the event, it was Sakhee who represented the stable at Epsom with Millenary traveling to Chantilly for the Prix du Jockey-Club where he finished unplaced behind Holding Court.
The race reflected the betting, with Millenary taking the lead two furlongs out, being briefly headed by Air Marshall in the closing stages, but displaying superior stamina to stay on under pressure and win by three-quarters of a length.
His best victory in 2001 came on his debut in the Jockey Club Stakes, at Newmarket where he recorded comfortable win over Sandmason with Holding Court third and Air Marshall tailed-off in last place.
[10] The race led the BBC to suggest that he would be "a force to be reckoned with", while John Dunlop called Millenary "a lovely character and... a good ride".
[12] After the race he was a leading fancy for the King George VI and Queen Elizabeth Stakes, but John Dunlop emphasised that the horse would not be risked on firm ground.
Millenary's last race of 2003, a short-head defeat to the double Champion Stayer Persian Punch in the Jockey Club Cup,[19] indicated the direction of his future career; from 2004 onwards, he was campaigned almost exclusively at long-distance events.
At York in August for the Lonsdale Cup he was held up in last place before quickening to lead and go clear inside the final furlong, beating the odds-on favourite Distinction by two and a half lengths.
Millenary has proved to be a successes at stud with a healthy 33% strike rate winners to runners ratio under both Flat and National Hunt codes.