Jersey beat hosts Guernsey by one run at KGV to take the top spot in the ICC European Division Two Championship.
Jersey chose to bat first and put on 218-5 in their 50 overs with Ryan Driver scoring the first century of the tournament finishing on 113 not out.
Guernsey were on course to win before a tail-end collapse saw them lose five wickets for only five runs.
A despondent Guernsey captain Stuart Le Prevost told the BBC: "We were in a winning position and threw it away."
With both teams having beaten Croatia, France, Germany and Gibraltar the winner of this game would be the division two champions.
Jersey captain Matt Hague helped his team to their total with 35, before he was caught at point by GH Smit, and was as surprised as he was pleased by the victory.
"It was one of the craziest games you'd ever play in," said Hague.
"We were out of that game for the whole time in the field. Guernsey were batting beautifully and really I thought they just had to bat and we'd lost the game, but we showed some ticker and what a fantastic effort.
Ben Febrache is run out
"We never gave in and we got there - unbelievable!"
The last ball of the game saw Guernsey, with one wicket remaining, needing two runs to draw the match which would have seen them win overall on net run rate but the Jersey field converged on Blane Queripel, containing him and Gary Rich to scoring one run.
Guernsey's top-scorer was Lee Savident with 98 and Le Prevost was keen to look on the bright side of how the team had performed.
"We were on course right the way through. Wickets lost was the key for us," he said.
"Credit to the Jersey bowlers, they bowled well, they fielded well, they kept the pressure on all the time, but we've only got ourselves to blame.
"It all bodes well for the future, we've got a young side so hopefully they'll come through and do the business in the years to come," the Guernsey captain added.
Jersey now go on to face Norway in a play-off for a place in ICC European Division One, but plans to change the World Cricket structure might make this unnecessary.
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