Time after time the San Marino rider used the Derbi's prodigious power to draw alongside the Honda coming out of the last turn and, although Poggiali insisted on sitting up well before the first corner, it looked likely that he would be able to out-drag the reigning champion at the same spot on the final lap.
Then, to complete Derbi's miserable afternoon, the engine on Poggiali's bike let go with seven laps to run, leaving a distraught rider unable to believe what had happened as he crouched by his stricken machine, beating the fairing in frustration.
Alzamora now had a comfortable three second advantage and, with Locatelli rolling off his lap times to ensure that he finished with a good point score, the top two was assured unless mechanical problems intervened.
Focus then switched to the scrap for the final podium position, with Arnaud Vincent making the most of a good starting slot to head a group of four riders battling for the silverware. The Frenchman's rival included Masao Azuma, Lucio Cecchinello - up from 17th on the grid - and Locatelli's Aprilia team-mate Simone Sanna, however, and things were not easy.
With the exception of Sanna, all three riders took turns to head the group into turn one, with Azuma and Vincent both making up places hand over fist by slipstreaming each other down the long home straight. The battle seemed set to go to the wire until Azuma dropped it heading into turn two for the very last time, delaying Sanna in the process, and setting up a two-way fight to the flag. The better power of the Aprilia ensured that Vincent took the spoils, as Cecchinello settled for a second consecutive fourth place.
Missing from the action already were the respective team-mates of Azuma and Cecchinello, after Mirko Giansanti and Nobby Ueda crashed out before half-distance. Neither rider, like Ui, was hurt, but both saw their distant championship chances further damaged as they slid harmlessly into the gravel.
With Alzamora and Locatelli taking the top two steps of the podium, and Ui failing to finish, the championship has taken another twist which sees the Italian back on top, and his Spanish rival closing in in defence of his crown. Fifteen points now separate Locatelli from Ui, with Alzamora and further 14 in arrears.
Round 13 in Valencia could be very exciting indeed.