CHELTENHAM, England : Poniros, a 100/1 jumps debutant owned by the big-betting chairman of Premier League Brighton & Hove Albion and ridden by a jockey who had planned to be elsewhere, stunned Cheltenham with an opening win on Gold Cup Friday. Trained by Willie Mullins, former flat racer Poniros pipped Lulamba (11/4) and favourite East India Dock (5/4) in a fourth successive Triumph Hurdle success for the Irishman. He was the longest-priced winner in the history of the Grade One race for