Billed as the novices' Gold Cup, the RSA Chase was expected to be fought out by last year's World Hurdle runner-up Punchestowns and the promising ex-french gelding Long Run.
The Willie Mullins trained Citizen Vic attempted to make all of the running at a steady pace, and with three to jump all nine runners were still in with a chance.
Both Punchestowns and Long Run were never jumping with any fluency and the writing was on the wall for the former as they approached the penultimate fence.
Citizen Vic took a crashing fall at the second last when struggling to hang on to his lead, and just when Long Run appeared the most likely winner, Weapon's Amnesty swooped on the outside and soon put the race to bed, sprinting home to record a seven length victory.
The 10/1 shot was recording his second Festival triumph after winning last year's Albert Bartlett Novices' Hurdle.
The win was compensation for trainer Charles Byrnes who saddled the disappointing Solwhit in yesterday's Champion Hurdle.
All being well the winner will attempt a Festival hattrick in 2011 and is a best price 12/1 for the Gold Cup with Paddy Power and Blue Square.