Luke Wright appeared to have batted Hampshire to the verge of submission – but less than three hours later the Royals were heading for Lords.
The former England man’s stunning 122 off just 100 balls – including 15 fours and three sixes – put Sussex Sharks on top in Saturday’s semi-final at Hove.
With 28 overs gone, the hosts were 159 for one and seemingly on course for a total approaching 250.
But for the remainder of the afternoon the visitors were in complete control.
After Chris Nash (26) and Matt Prior (28) had helped Wright get the Sharks’ innings off to a flier, no-one else passed 10 as the Royals slammed on the brakes.
Danny Briggs (two for 32) picked up his second wicket of the day to remove Ed Joyce for a duck and David Griffiths (two for 67) accounted for Murray Goodwin (10) as the collapse began.
But the 35th over was the real turning point as Sean Ervine grabbed three wickets in six balls, removing Wright, Ben Brown (nought) and Kirk Wernars (one).
Michael Yardy (one) followed at the end of the next over – becoming Griffiths’ second victim as the stumps were spread-eagled.
And, with eight wickets down, Will Beer and Steve Magoffin had little choice but to guide the hosts through to an under-par 219 for eight.
Ervine’s three for 36 was the pick of the bowling, while Chris Wood (one for 46) grabbed the crucial scalp of England star Matt Prior.
The momentum had switched – and Hampshire openers Michael Carberry and James Vince immediately hammered home the advantage.
A stunning 129-run opening stand came in less than 13 overs as the pair ran riot.
Carberry bludgeoned 68 off 36 balls, while Vince’s 58 from came off 42 balls and included 11 fours.
Sharks’ spinner Beer did for both men – Carberry caught at long-on and Vince bowled 10 balls later.
But Jimmy Adams (44 not out) and Simon Katich (47 not out) had time to play themselves in before pressing on to see the visitors over the line with seven overs to spare.
The eight-wicket win sets up a final clash with Warwickshire on Saturday, September 15.