HAPPY Guy's Derby credentials received a significant boost yesterday with a scintillating Sha Tin gallop. Brian Kan Ping-chee's Classic Trial winner came away from last year's Derby hero Sound Print and stablemate and fellow Derby contender Right Way at the end of their searching work. They clocked an excellent one minute 12.3 for their 1,200-metre gallop which confirmed that Happy Guy's defeat of Deerfield in the Classic Trial was no fluke. Respected Irish trainer Tommy Stack once held out very high hopes for Happy Guy and it could be that he is only now coming right. On this work he must enter serious Derby calculations along with Deerfield and Charming Talker, not least because the way he pulled ahead over the last 50 metres suggested that he will be able to handle the step up from a mile to 1,800 metres. But Sound Print's work was nowhere near as well as he was going before beating River Verdon in the Stewards' Cup and he cannot be backed with confidence in tomorrow's Sandown Park Challenge Cup despite a number of his rivals being out of the handicap. There was good work from Lawrie Fownes' last-start winner, Innovation, in readiness for his clash with Sound Print. He appears to have improved since his recent defeat of Busy Win over course and distance. Gary Ng Ting-keung's pair of Smile For Me and Maniwin worked really well for Tony Cruz in preparation for the opening and third events. There was a strange piece of work from Northern Fire Ball who will be strongly supported for the seventh. He was brilliant in a recent trial but yesterday he went past lowly-ranked stablemate Great Dancer only for that one to rally and kick back to the front. Southern Glory has been flying in the mornings and could go well against Smile For Me in the first.