Glamorgan 190 for 5 (Douthwaite 51*, Root 38*) beat Kent 155 (Stevens 34, McIlroy 3-31) by 35 runs
Glamorgan have thrashed the Kent Spitfires by 35 runs in their final Vitality Blast game of the season at Canterbury.
Qais Ahmad took two for 36, but dropped catches and indifferent bowling that gifted the visitors 20 extras meant the total was at least 30 runs higher than it could have been.
James McIlroy then took three for 31 as the Spitfires were bowled out for 155, Darren Stevens the top scorer with 34. The defeat means the reigning champions finish bottom of the South Group just a year after winning the competition.
A crowd of around 3000 witnessed the dead rubber at the St Lawrence, with Glamorgan unable to finish higher than sixth and Kent looking to avoid matching their worst-ever Blast season, when they won just three matches in 2013.
The visitors chose to bat and were 46 without loss at the end of the powerplay, but lost Tom Bevan for 21, lbw to Qais attempting to reverse sweep, before Matt Milnes bowled Sam Northeast for 33.
Qais switched to the Nackington Road End and immediately bowled Chris Cooke for one and Colin Ingram was out for 26 when Grant Stewart sent his off stump flying.
Jack Leaning then had Eddie Byrom caught by George Linde at backward point for a second ball duck but Qais's final over, the 16th, was expensive, going for 16, including a reverse swept six by Root.
The indifferent fielding that has dogged Kent throughout their Blast defence continued with two drops in Milnes' 17th over. Root skied one to Tawanda Muyeye, who seemed blinded by the late evening sun, before Douthwaite was spilled by an inrushing Leaning.
The 19th over had a whiff of Stuart Broad's record-breaking calamity at Edgbaston the previous day. Root hit Milnes' first ball for six and was then caught by Muyeye off a no-ball. A further no-ball and five wides saw the Welsh side cash in with 22 from the over.
Fred Klaassen's final over was nearly as gruesome, going for 19 and Kent's chase got off to an equally dismal start when Joe Denly was run out by Root in the first over.
Muyeye cracked three elegant boundaries but then swiped McIlroy to Byrom and was out for 13, before Jordan Cox fell for one, pulling James Weighell to Ingram at mid-wicket.
Alex Blake hit his 100th Blast six when he hammered Douthwaite over cow corner, but when Leaning chipped a return catch to Salter for 10 Kent, were 46 for four.
Stevens' return after a lengthy injury lay-off produced the biggest cheer of the night but this was a rescue act beyond even him, although he did flick Prem Sisodiya for a six that nearly cleared the flats on the Old Dover Road side.
Blake went down swinging for 32, skying a Salter delivery to Northeast and Stevens' cameo ended when he hit a Douthwaite full toss to Bevan on the boundary.
Stewart offered some fight with 23 from 10 before he hit Sisodiya to Bevan and Qais had his stumps splayed by McIlroy for four. McIlroy then had Linde caught by Root for 21 and Glamorgan's victory was sealed when Milnes hit Douthwaite to long off and Bevan held his third catch of the innings.