Warrior springs 25/1 shock
Regal Warrior scores under Liam McKenna
(Healy Racing Photos)
The James Lambe-trained gelding travelled well to lead two furlongs out in the mile-and-a-half contest.
McKenna, claiming 7lb, only had to keep his mount going in the closing stages to record a cosy length-and-a-quarter success over Silver Shuffle.
The winner was having his first run on the Flat since August 2009 but had been a decent fourth over hurdles at Ayr last time.
McKenna is the stepson of trainer Lambe and was partnerning his second winner, first on Flat, having rode Yachvili to success over hurdles at Downpatrick nine days ago.
"He's a cool kid and he's learning his trade," said Lambe.
"The horse has been unlucky as he never got his ground over hurdles. On his form here before you could give him a squeak tonight.
"He's a strong traveller and the only thing that's been catching him out is the ground.
"He wants an easy two miles on good ground. We'll come back here again and Liam will claim off him again."
Winning owner James Callow travelled over from England to witness tonight's success.
Everything Zain, who had been in good form over hurdles, was a well-supported 13/8 favourite but couldn't get involved in tenth.
(Additional reporting by Michael Graham)
The complexion of the race changed in the dying strides in the second division of the mile handicap at Dundalk as Clare Harrier powered home to lead on the line.