Trojans snatched a last-gasp penalty equaliser before beating City of Portsmouth 5-3 on 'flicks' and clinch a place in next Monday's (3.45pm) Hampshire Cup final against Havant at Chapel Gate.
With less than a minute remaining, Trojans were trailing 2-1 to a City side that had beaten them in last season's Sports Centre final.
But City goalkeeper Chris Ball conceded a penalty when he mistimed a challenge on Chris Wiseman - and Wayne Shepherd earned Trojans a reprieve by burying his shot in the bottom corner.
Trojans thrived on a 'miss' by City's Chris Boyland and converted all five flicks in the shoot-out.
Portsmouth led 1-0 at the break through former Winchester striker Greg Cox, but earlier missed a penalty when Steve Turnbull sent a flick wide.
The balance of power changed when City's Mark Cheshire left the field to visit his expectant wife in hospital.
Trojans had struggled to asert themselves during the opening period, but with Cheshire departed, found more space after the break and twice went close before Chris Wiseman got the finishing touch in a goalmouth melee to make it 1-1.
Paul Hilton made one stunning run and Ball made several fine saves as Trojans sought a winner.
But, after chances had gone begging, it was City who looked to have snared victory when university student Paddy Fisher converted a low ball in from the right by Cox.
With the umpires checking their watches, Shepherd bagged a dramatic penalty flick equaliser.
Hilton, Colin French, John Jauncey, Duncan Stewart and Shepherd converted their 'extra-time' flicks, while Boyland's miss proved fatal.
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