Sussex's totesport League promotion hopes were brought to an agonising halt by three audacious strokes from 19-year-old Durham paceman Liam Plunkett at Riverside.
The county went down by two wickets after rain brought the Duckworth Lewis method into play.
Robin Martin-Jenkins had figures of 3-10 in four overs when he began the final over with Durham needing 15 with two wickets standing.
Neil Killeen took a single off the first ball, then Plunkett amazingly drove the next three for four, six and four.
The first two blows were in the direction of long-on before a straight drive sealed Durham's win.
Plunkett, named last week as one of those who will attend the England Academy part-time this winter, also bowled a very lively opening seven-over spell and produced a superb piece of fielding which brought a crucial run-out.
On a pitch offering more pace and bounce than usual at Riverside, Sussex elected to bat and made 214-7, five more than the previous top totesport total at the ground this season.
Martin-Jenkins then bowled Gary Pratt with the last ball before rain arrived, leaving Durham on 69-3 after 14.3 overs. After the loss of 17 overs Durham were given a revised target of 159, which meant they had to score 90 off 13.3 overs.
Gareth Breese cut at the first ball from Martin-Jenkins on the resumption and edged it to wicketkeeper Matt Prior.
Home skipper Jon Lewis then put on 59 in 9.3 overs with Gavin Hamilton before both fell in the space of five balls. Lewis was bowled on the back foot by a Mushtaq Ahmed googly for 48, then Hamilton was lbw for 27 when trying to reverse sweep Mark Davis.
Durham needed 26 off three overs and when Martin-Jenkins returned and pinned Graeme Bridge lbw with his first ball it looked all over, especially as only three runs came off the over.
The next, from James Kirtley, yielded eight and it seemed all Martin-Jenkins had to do was keep bowling just short of a length.
But he was as unaware of Plunkett's capabilities as the Durham fans, who were astonished by the way things unfolded.
Two excellent pieces of fielding produced the run outs which checked Sussex when they looked like making a bigger total.
Ian Ward and Michael Yardy were stepping up the tempo after putting on 93 in 22 overs for the second wicket when Durham struck two vital blows.
Yardy was run out for 46 by an athletic pick-up and throw to the non-striker's end from Plunkett coming in from the cover boundary, then Chris Adams top-edged a reverse sweep to short fine leg.
From 107-1, the loss of two quick wickets left Ward and Murray Goodwin to rebuild with a stand of 46 in nine overs.
Again, just when they were looking capable of pushing on, a run out helped restrict them to 62 off the last ten overs.
Ward had hit eight fours in making 72 off 97 balls when he called Goodwin for a single to deep gully from the nonstriker's end. But he failed to beat the direct hit after Gary Pratt swooped from backward point.
Goodwin hit only one four, a cut off Breese, in making 35 off 50 balls before he drove Killeen to Pratt at long-on in the 42nd over.
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