Yardy made a composed unbeaten 13 and shared 22 with Ravi Bopara, but the Essex batsman was caught in the deepand with both sets of fans in fervent mood, Gul bowled the final over.
Sussex managed to prevent a boundary being scored in the final four overs, but a rasping Hughes swipe was dropped by Joyce at mid-wicket and Henriques reached fifty in the final over when Chawla spilled a difficult chance in the deep.
However, the Pumas' limited match plan of swamping the opposition with deep kicks and relentless forward play finally came unstuck against a South Africa side who go into next weekend's final as favorites to stop England's bid to become the first nation to retain the title.