Ryan Moore looked to have stolen a march on the rest of the field on Aidan O'Brien's highly experienced Harpocrates (7/1) as they entered the final furlong, but Valdermoro (9/2) made up ground rapidly under Tony Hamilton to get up close home and score by a neck.
Third went to 25/1 chance Ropey Guest.
It was a first win in the Acomb for local Malton handler Fahey, who will now consider some loftier targets for the son of Declaration Of War, who has entries in the Champagne Stakes at Doncaster, the Royal Lodge and the Dewhurst.
Fahey said of the recent Doncaster scorer: "It was nice to see him go and do it again. I was worried that Ryan had nicked it, but we do like our fellow. I'm sure he'll get further as well.
"He'll have some big entries now and I'm sure he'll be taking up one of them. We'll see how he is but he's not a horse I'd like to run on too soft ground. I probably shouldn't say that as you never know but he's such a good moving horse.
"We've always liked him, I just felt today the seven furlongs might have been sharp for him and if you look he was over by the stable gate when Tony was able to pull him up. He's pretty smart and I like him a lot. One day he'll be a proper horse."
O'Brien said of the runner-up, who seemed to thrive in first-time blinkers: "I'm delighted, he ran a really good race.
"He's a horse that is still progressing, but I'm delighted with his run really."
