In September 2004 the yearling was consigned by Barronstown to the Goffs sales and was bought for €220,000 by Coolmore's bloodstock agent Dermot "Demi" O'Byrne.
[3] His dam Caladira who was bred and owned by Aga Khan IV won on her racecourse debut and finished unplaced on her only subsequent start.
[5] Septimus began his track career in a seven furlong maiden race on 10 September on Leopardstown Racecourse in which he was ridden by Wayne Lordan and won by half a length from his stablemate Arabian Prince.
Ridden by Seamie Heffernan, he tracked the leaders before taking the lead inside the final furlong and won by a length from Rekaab.
[7] Two weeks after his win at the Curragh, Septimus was sent to England and moved up in class and distance for the Group 1 Racing Post Trophy over one mile on heavy ground at Doncaster Racecourse.
On 23 April Septimus began his second season with a trip to France for the Prix La Force over 2000 metres at Longchamp Racecourse in which he was well-fancied, but never looked likely to win and finished seventh of the nine runners behind Barastraight.
After tracking the leaders he went to the front a quarter of a mile from thefinish and drew right away from his opponents to win by eight lengths from the Michael Stoute-trained Best Alibi.
[9] On 3 June Septimus joined Horatio Nelson, Dylan Thomas and Mountain in a four-horse Ballydoyle entry for the Epsom Derby and started the 17/2 fourth choice in the betting.
Septimus raced in second place behind Championship Point before taking the lead approaching the final furlong and won by one and a half lengths from Fracas.
Ridden by Johnny Murtagh, Septimus ranked in third place for mot of the way before taking the lead approaching the final furlong and winning by a neck from Balkan Knight.
Ditinction and Balkan Knight were again in opposition but his most serious rivals appeared to be Allegretto (Goodwood Cup) and Geordieland (Grand Prix de Chantilly).
Septimus made steady progress, overtook Finalmente approaching the last quarter mile and accelerated away from his rivals to win "easily" by five lengths.
[16] Septimus was off the track for nine and a half months before returning in the Group 3 Curragh Cup over 14 furlongs on 28 June 2008 in which he carried 140 pounds and started the odds-on favourite.