Gloucestershire 157 for 5 (Cockbain 62*) beat Middlesex 179 for 5 (Cracknell 67) by two runs (DLS method)
Ian Cockbain hit his first half-century of this year's Vitality Blast to earn Gloucestershire a narrow win over Middlesex after rain at Radlett prevented a nail-biting finish.
Cockbain, who top-edged the final ball of the 18th over from Steven Finn for six, did just enough to edge his side ahead by two runs under Duckworth-Lewis-Stern calculations. Until then, Gloucestershire had been behind the required rate, but Cockbain and Ryan Higgins, with an unbeaten 20, did enough to tilt the contest in their favour, reaching 157 for 5 when a downpour halted play.
The run chase was controversial, with both captains questioning the decision to start a fixture at an outground - without floodlights - as late as 5.30pm. Middlesex were told to bowl spin at one stage due to poor light, leading to prolonged delays while Eoin Morgan spoke to the umpires. They brought Finn back in the 18th over, though he conceded two sixes to tilt the game in Gloucestershire's favour.
"The more frustrating thing from my side was that it was so dark, so early," Morgan said. "The fact that you're forced to bowl spin, as a captain, when it's probably not the best option to do so at that time. That happened in about the 12th over and in a game of T20 cricket your hand is forced.
"The light was questionable the whole time, but there are two very experienced umpires out there and you have to trust their decision. Given the situation we found ourselves in, the right decision was made. It was dark by the end of the game and when it's dark, safety comes into it."
Jack Taylor, Gloucestershire's captain, said: "The umpires were stuck between a rock and a hard place - it did get pretty dark early on. In white-ball cricket, you try and stay out there and they obviously wanted to keep a full game, but I think to be honest a lot of it's down to the start time.
"I don't think we can play at half past five any more, without lights. Ultimately we all want to play full, good games of cricket and that tarnished some of the good cricket we played in the first half. We had a similar thing at Glamorgan last week - the floodlights weren't working so we started at 5.30 and the last half-hour of the game was too dark."
Middlesex had posted 179 for 5 after being put in, built around Joe Cracknell's 41-ball innings of 67 - the youngster's second successive half-century.
The home side struggled to find momentum in the powerplay and lost Paul Stirling for just 8, slamming Josh Shaw into the hands of mid-off. However, Cracknell looked assured at the crease, punching the ball cleanly and finding the boundary regularly as he and Stephen Eskinazi added 59 from 45 balls.
Tom Smith broke the partnership, luring Eskinazi down the track for Glenn Phillips to pull off a stumping, but Cracknell advanced past 50 before mistiming his drive off Dan Worrall and picking out the long-off fielder.
Higgins squandered a chance to dispose of Morgan early, dropping him at point - and the Middlesex captain made him pay, thrashing 21 off his next over as he raced to 38 from 22 balls. Higgins got his man eventually, caught in the deep after a knock that included three sixes, before a late flurry from Chris Green, who hit 13 not out from six deliveries, lifted Middlesex to 179.
Gloucestershire got away to a flying start courtesy of Chris Dent, who took three successive fours off Tim Murtagh and dispatched Blake Cullen for two sixes to reach 32 from just 15 balls.
Despite the departure of Dent - tempted by Steven Finn's short ball - the visitors reached 61 for 1 in the Powerplay and Cockbain maintained the scoring rate with a succession of boundaries. However, spin duo Green and Luke Hollman, who finished with figures of 2 for 30 and 2 for 33 respectively, slowed Gloucestershire down during the middle overs with flight, variation - and a clutch of wickets.
The pick of those was Morgan's grab at short cover to dismiss Benny Howell off Hollman, but Cockbain remained to marshal the chase and ultimately did just enough to secure Gloucestershire's victory.