Gloucestershire 254 for 3 beat Middlesex 149 for 8 by 105 runs
A stunning 44-ball century from Kevin O'Brien helped Gloucestershire post the highest total in domestic T20 cricket and move off the foot of the Friends Life South Group after overcoming fellow-strugglers Middlesex by 105 runs at Uxbridge.
The Gladiators racked up 254 for three against a toothless Panthers attack - beating the 250 for three recorded by Somerset, against Gloucestershire, at Taunton in 2006.
They were also only four runs away from equalling the world record set by Sri Lanka against Kenya in the 2007 ICC World Twenty20 .
Irish World Cup star O'Brien crashed 119 off 52 balls and Hamish Marshall hit 102 in 54 deliveries as the Gladiators became the first side to boast two centurions in the same T20 innings.
O'Brien, whose previous best in domestic Twenty20 cricket was 39 not out, revived memories of his thrilling 113 against England in this year's World Cup as the 27-year-old Irishman made the most of being dropped on 14 and 33 to bring up his fifty from 23 balls.
He motored to his hundred in just 44 deliveries in the 13th over, and moments later Marshall, who had also been dropped on 21, moved on to a 33-ball half-century.
The pair enjoyed an opening stand of 192, a new record for any wicket in domestic Twenty20 cricket, before O'Brien holed out to long-on and walked off to standing ovation having struck a total of 11 sixes and seven fours.
Marshall simply picked up where O'Brien left off, raising his hundred - off 53 balls - with the third of three successive fours off Anthony Ireland in the 19th over, although not before Williamson had been caught on the deep point boundary.
When Marshall eventually lobbed a catch to mid-on, he too received a rousing reception having hit four sixes and 11 fours in his 102.
In the face of such a daunting total, Middlesex crumbled to 15 for three in the fourth over before making a recovery of sorts thanks to Dawid Malan, the Panthers acting captain, who hit 32 before he was stumped off Ed Young.
John Simpson made a plucky 38 off 27 balls and Tom Smith struck an unbeaten 36, but by that time the result was never in question. The Panthers eventually mustered 149 for eight, with Jon Lewis taking 3 for 31.