Leicestershire 307 for 8 (Pettini 92, Cosgrove 91) beat Lancashire 176 (Smith 56, Dexter 4-22) by 131 runs
Leicestershire won their first Royal London Cup match since August 2014, hammering Lancashire by 131 runs at a startled but delighted Fischer County Ground to move above the visitors at the bottom of the North Group table.
Fine innings by Mark Pettini and Mark Cosgrove, and List A career-best bowling from Neil Dexter, were the highlights of an extraordinary match, the result of which has probably ended Lancashire's chances of reaching the quarter-finals.
Put in by Lancashire captain Steven Croft, Leicestershire's innings began steadily. Former Lancashire opener Paul Horton hit five boundaries in scoring 32 before going back to a delivery from Tom Smith that stayed a little low and being dismissed leg before wicket.
Cameron Delport made a fluent 25 before edging an attempted drive at Jordan Clark, but from 93 for 2 Pettini and Cosgrove built the innings' most substantial partnership by some distance. Initially watchful, Cosgrove became increasingly punishing, mixing powerful straight blows with a series of delicate cuts and deflections square on the off-side, while Pettini too accelerated in impressive style.
The Leicestershire captain was on 92, and looking set for his first one-day hundred since joining from Essex, when he tried to clip a straight delivery Smith to midwicket and went leg-before.
Cosgrove also looked set for a century, but hit Nathan Buck high to long-off where Croft fell back over the boundary as he caught the ball above his head, but had the presence of mind to toss it back over the ropes as he did so, and the athleticism to then scramble back and catch the ball again before it hit the ground.
Lewis Hill and Michael Burgess followed in short order, but Dexter hit Stephen Parry for consecutive sixes and Niall O'Brien also hit out to good effect as the Foxes dragged their score past 300 - competitive, but not intimidating on a flat pitch facing a Leicestershire attack lacking strike bowler Clint McKay.
The target looked even more achievable when Smith and Alviro Petersen were adding 74 for Lancashire's first wicket, in just under 14 overs. In the circumstances Petersen's decision to attempt to reverse sweep the offspin of Rob Sayer was questionable, the more so as he both missed the shot and dragged his back foot out, and O'Brien took off the bails with some relish.
The introduction of Dexter's medium-pace increased Lancashire's problems, though Karl Brown had only himself to blame as he pulled a short ball into the hands of Ollie Freckingham at deep square leg. Smith looked in outstanding touch, hitting eight fours in going to 50, but remarkably then became Horton's first victim in List A cricket.
Horton had not previously bowled a single delivery in 105 List A matches, but was thrown the ball by Pettini and saw Smith's mistimed attempt to hit his third ball over long-on give Hill a catch.
Dexter then bowled Luke Procter and ended Liam Livingstone's frenetic innings with an outswinger that found the edge. The writing was on the wall when Delport picked up two wickets in as many balls, Horton catching Clark at long-on before Croft, attempting to drive, inside-edged the ball on to his stumps.
Dexter trimmed Kyle Jarvis's off-bail and Dieter Klein, making his first team debut for the Foxes - the South African left-armer is on trial with the county - ended the match by having Tom Moores caught by Cosgrove at extra cover.