He showed some promise in his early career but emerged as a top-class performer in 2004 when he won the Royal & SunAlliance Chase at Cheltenham Racecourse in England and the Grande Course de Haies d'Auteuil at Auteuil Hippodrome in France.
He made only two appearances, finishing a close fourth at Leopardstown in January and fifth, beaten thirty lengths by Adamant Approach at Cork Racecourse in April.
Ridden by David Casey made steady progress over the last six fences before overtaking his better-fancied stable companion Hedgehunter in the closing stages and winning by three and a half lengths.
[7] In the last race of his spring campaign, Rule Supreme started 4/7 favourite at Gowran Park but fell at the eighth fence when in third place.
After a break of more than six months, Rule Supreme returned at Thurles Racecourse in December when he won the Glen Chase, beating more experienced rivals by four lengths when ridden by Ruby Walsh.
Rule Supreme did not jump well and was towards the rear of the field for most of the way, but began to make progress approaching the second last fence where Mossy Green fell and brought down Pizarro.
[10] Rule Supreme returned to England again in April, unseating Casey when he made a bad jumping mistake in the Mildmay Novices' Chase at Aintree, and finishing fifth when carrying 164 pounds in the Betfred Gold Cup at Sandown Park on the last day of the season.
Four days after his defeat at Sandown, Rule Supreme started a 20/1 outsider and finished fifth of the six runners behind Beef Or Salmon in the Grade I Punchestown Gold Cup.
Three weeks later he faced Great Love and Nickname again, as well as the leading steeplechasers Kotkijet and Batman Senora in France's most important hurdle race, the Grande Course de Haies d'Auteuil over 5100 metres.
[11] Mullins was unable to attend, after contracting food poisoning on his previous visit to France but John Lynch, the gelding's owner was reportedly "ecstatic", saying "They said that Kotkijet was unbeatable!
"[12] In the autumn of 2004, Rule Supreme was campaigned in long distance hurdle races, beginning with a win under top weight of 165 pounds in a handicap at Clonmel Racecourse on 18 November.
He returned to steeplechasing later in the month for the Lexus Chase at Leopardstown in which he was matched against Beef Or Salmon and the three time Cheltenham Gold Cup winner Best Mate.
On 6 February 2005 Rule Supreme met Beef Or Salmon again in the Hennessy Cognac Gold Cup over three miles on soft ground at Leopardstown and was made the 11/2 second favourite.
He finished unpaced behind Hi Cloy in the Grade II Kinloch Brae Chase at Thurles in January and was last of the eight runners behind The Listener in the Hennessy Gold Cup a month later.