Septimus gave Aidan O'Brien a remarkable eighth victory in the Juddmonte Beresford Stakes at the Curragh but had to work to land the odds in the Group 2 contest.
Seamus Heffernan took over from Kieren Fallon on the well-regarded son of Sadler's Wells and had to get serious late on to settle matters.
The 4/6f squeezed through to challenge Rekaab before the furlong pole but took time to get into top gear. He answered Heffernan close home, however, and quickened nicely in the last 100yds to secure victory by a length.
'He has learnt a lot today. He got hampered a bit in running. There is maybe no need to run him again now as he learnt so much here,' said the winning trainer afterwards.
O'Brien also revealed that Fallon, who was absent from the meeting, was 'recovering from food poisoning in America.' Cashmans make Septimus a 20/1 shot for next year's Derby.
Alexander Alliance looked a nice prospect for next year's 1,000 Guineas when landing the Listed Flame Of Tara Stakes earlier on the card.
The Tommy Stack-trained filly burst through to lead at the furlong pole in the six-furlong event and easily accounted for Kamarinskaya by three-and-a-half lengths.
Michael Halford and Johnny Murtagh began the day in great style, claiming the first two races with Cupids Ray and Miss Sally.
Cupids Ray led inside the final furlong to claim the opening K&M Timber Handicap by three-parts-of-a-length from Scripted.
The quick brace was completed when Miss Sally wore down Majestic Times in the final furlong to claim the Listed Leinster Leader Waterford Testimonial Stakes.
The John Oxx-trained Allexina proved much too good for English raider Foreign Affairs when running out an easy five-length winner of the Listed Rathbarry Stud's Barathea Finale Stakes.
Clara Allen (5/1f) was the buzz horse in the Hackett's Bookmakers Irish Cesarewitch and duly collected in good style, beating Mrs Gillow by two lengths.
Trainer John Quinn capped a good week when Bricks And Porter landed the Derrinstown Stud Apprentice Handicap Final under Stephen Hunter.
Paul Carberry was seen at his brilliant best at Limerick as Star Clipper flew home in the closing stages to claim the Anglo Irish Bank Munster National.
Carberry conjured a late burst from the gelding to collar Pearly Jack close home and score by a length-and-a-half in the 100,000 contest.
Watson Lake gave Carberry and trainer Noel Meade a double when running out a comfortable winner of the Sherry Fitzgerald O'Malley Chase.
Chasing debutant Accordion Etoile was set to challenge, before a bad blunder at the second last, and had to settle for a highly promising second.
Mossbank looked a smart prospect when making a winning debut over hurdles in the opening Newenham Mulligan Novice Hurdle while Sky's The Limit bounced back to form to run out an easy winner of the Michael Punch & Partners Hurdle.
