Leicestershire 324 for 4 (Smith 135*, Cobb 130) beat Somerset 323 for 3 (Trego 118, Petersen 63*, Trescothick 57, Buttler 54*) by six wickets
Openers Josh Cobb and Greg Smith both hit centuries as Leicestershire beat Somerset by six wickets in a spectacular run-laden Yorkshire Bank 40 clash at Grace Road.
Somerset, who had won their first three games in the competition, posted 323 for 3 with Peter Trego hitting 118 and Marcus Trescothick, Alviro Petersen and Jos Buttler weighing in with half-centuries.
However, Leicestershire responded by scoring 324 for 4 to win the game with seven balls to spare, thanks largely to the efforts of Cobb and Smith. The duo set up the record-breaking run chase with the club's biggest-ever opening partnership in one-day cricket, putting on 235 in 25 overs to beat the previous best of 228 by Phil Simmons and Vince Wells against Kent in 1996.
Cobb's 130 was his second successive century in the competition this season while Smith, brought in only because Niall O'Brien was away playing for Ireland against Pakistan, hit a career-best 135 not out. Leicestershire's previous most successful run chase was against Durham when they scored 289 for victory in 1996.
Captain Cobb, who made 107 in the first game of the season against Gloucestershire, again led from the front reaching a half-century off 35 balls with 10 fours. Smith matched him shot for shot, taking only 27 balls for his 50 with eight fours and a six.
The boundaries continued to flow as the two batsmen put Somerset's attack to the sword, Cobb moving to his century off 62 balls with 16 fours and a six. The 200 stand came up in the 20th over, but with the record partnership established Cobb was yorked by Steve Kirby for 130 off 87 balls.
Joe Burns, Ned Eckersley and Matt Boyce all went cheaply as Leicestershire stuttered. However, it was only a temporary blip with Shiv Thakor joining Smith in a fifth-wicket stand that produced 46 runs and a stunning victory.
It was difficult to believe that Somerset's innings could be eclipsed after some great batting that saw Trescothick (57) and Trego put on 120 in 15 overs for the first wicket. Trego, finally caught in the deep off Nathan Buck, hit 118 off 100 balls with 15 fours and a six while Petersen (63 not out) and Buttler (54no) shared a fourth-wicket stand of 82 in the last seven overs.
It was the second time in four games this season that Somerset had topped the 300 total. Incredibly, this time it was not enough.