Surrey 171 for 7 (Jacks 63, Qayyum 3-22) beat Kent 170 for 3 (Bell-Drummond 64, Crawley 59) by 1 run
Kent Spitfires suffered their second batting calamity of the week as they tossed away a winning position to lose their Vitality Blast South Group qualifier to Surrey by one run at shell-shocked Canterbury.
Just three days after being skittled for 40 in a County Championship defeat to Essex, Kent grabbed defeat from the jaws of victory to suffer their fourth reverse and their first on home soil in this year's T20 tournament.
Clark's misery was compounded when he dropped Bell-Drummond off a skier at cover in the next over from Jade Dernbach as Kent's openers posted 50 in five overs.
Crawley raced to his maiden T20 fifty with two fours and three sixes as the Spitfires pair posted their century stand in 9.5 overs as Kent swept 26 runs ahead of Surrey's midpoint score.
Bell-Drummond reached his 19th career T20 half-century from 32 balls and with seven fours but their stand was finally broken for 115 when Mohammad Tahir had Crawley stumped for 59.
With 18 required from 12 balls, Bell-Drummond went for 64 when his sliced drive against Dernbach flew to backward point to heap pressure on Alex Blake and Heino Kuhn.
Blake upper-cut his third ball to deep point leaving Sam Billings and Kuhn to score 12 off the last over from Sam Curran, but it was Curran who held his nerve by conceding nine off the bat to give Surrey a surprise fourth Vitality Blast win.
After a forceful start, Surrey stumbled mid-innings when Kent took pace off the ball, then plundered quick runs at the death through a barrage of Will Jacks sixes on their way to posting 171 for 7.
Aaron Finch, who hit 83 here last July at a strike rate of 218.42 - only for the match to be abandoned to rain - clattered 18 off the second over of the night from Kent T20 debutant Matt Milnes but, with 25 to his name, miscued a Fred Klaassen slower ball back to the bowler.
Surrey reached 49 for 1 by the end of the Powerplay, after which Spitfires brought on first-team debutant Marcus O'Riordan, a 21-year-old off-spinner whose excellent opening over cost only five runs.
Kent turned to spin at both ends with the introduction of left-arm spinner Imran Qayyum who had Curran caught at cow corner with his second ball.
Surrey lost further impetus when Bell-Drummond yorked Mark Stoneman, Qayyum squeezed one between the bat and pad to bowl Ben Foakes and then had Ollie Pope stumped by Ollie Robinson as Surrey raised their 100 in the 15th over.
Qayyum finished his four overs with 3 for 22, after which Hardus Viljoen returned to pluck out middle stump via a bottom edge as Clark aimed to cut.
Jacks clattered eight sixes late in the piece on his way to 63 off 27 balls before biffing Klaassen's last ball of the innings into the hands of long off, even so, Surrey's total appeared a little below par.