Owega Star stayed on dourly to land the Tara Hurdle at Navan after a dramatic conclusion to the Grade Two contest.
Peter Fahey's charge was hard ridden in a battle with Maller Tree two out, but both looked sitting ducks for Un Beau Matin, who was sent off the even-money favourite in the absence of Simenon and Muirhead.
However, the grey took a crashing fall when travelling well, leaving Owega Star (4-1) and Andrew Leigh in front, and he battled on gamely to account for Maller Tree by a length and three-quarters.
Fahey said: "He really deserved that. If you look back through his form he has never run a bad race.
"He'll probably only have one or two more runs this season as I can't wait for next year over fences - he's a brilliant jumper. I'd say the plan will be to bring him back good and early over fences.
"Andrew gets on with him really well. He's not the easiest horse to ride and can mess around and whip around at the start. This was our Derby day today."
The 'Prancer And Dancer' Handicap Chase went to Colm McBratney's Sole Witness (16-1) and he will now be aimed at the Thyestes Chase.