Gareth Batty took 4-14 in five overs as woeful Glamorgan were bowled out for just 83, losing the NatWest Pro40 play-off to Worcestershire by 103 runs.
Batting first on a slow, used wicket Worcestershire began steadily through Vikram Solanki's 53 at the top.
Moeen Ali then batted with great intelligence, injecting acceleration with a knock of 51 off 52 balls.
And Glamorgan's batsmen never recovered after three were dismissed in the first two overs of their run chase.
It was such an unseasonally warm day at Cardiff's Swalec Stadium that the only spectators who were not dressed in t-shirts were bare-chested.
But apart from soaking up the sun, there was little enjoyment to be had by the home fans.
Worcestershire won the Pro40 title in 2007 but found themselves in this scrap to retain their Division One status after finishing seventh in the table.
"We will strengthen the squad in the winter and we are currently in talks with Herschelle Gibbs for next season"
But after losing the toss and finding themselves in the field early on, they never reached a position of strength.
Worcestershire - despite scoring at barely four and a half runs per over - posted a more than useful target in fairly awkward batting conditions.
There was plenty of spin on offer for Dean Cosker, Robert Croft and Jamie Dalrymple, but of them only the experienced Croft was able to keep a lid on the scoring, while Dalrymple's four overs - in which he was hit for one huge six by Ali - cost 31.
Solanki was irritated when picking out deep midwicket with a slog-sweep off Croft, but the lower middle order combined well with Ali in the last few overs.
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The decision to have two pinch-hitters - Croft and David Harrison - in the top three was ripped to shreds when Dilhara Fernando removed both in the first over.
Andrew Harris then bowled beautifully to remove Andrew Harris and Michael Powell and at 18-4 the game was almost up long before Batty's wizardry had the final say.
Solanki said afterwards: "It's good to be in the top flight of both the Championship and the 40-over league next year.
"It was not your ideal one-day pitch, but Moeen played pretty well towards the end of our innings."
"English cricket's very strong and all the divisions are very tight, but it would have been very disappointing if we hadn't won today"
Glamorgan cricket manager Matthew Maynard said: "It's disappointing that our biggest crowd of the season haven't seen us at our best.
"There will be changes for next season. We have to have cricketers who have two or three of the cricket disciplines.
"Unfortunately today that was highlighted and ultimately it cost us. The senior players are responsible at the top of the order but unfortunately we haven't once got off to a good start in the competition this year.
"More often that not the middle order has had to rescue us but not today.
"We will strengthen the squad in the winter and we are currently in talks with Herschelle Gibbs for next season."
Gibbs played in the Twenty20 competition this summer, but with Jason Gillespie considering retirement the South African may now accept a deal to be the Welsh county's principal overseas player in 2009.
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