Glen Chapple claimed five wickets and Oliver Newby made key contributions with bat and ball as Lancashire secured a place in the Clydesdale Bank 40 semi-finals with an 18-run win over Gloucestershire at Bristol.
Evergreen captain Chapple returned 5 for 26 as the home side were bowled out for 164, James Fuller making a valiant 43. But Newby was equally responsible for his side's success.
First the 27-year-old seamer top-scored with 36 not out, batting at No. 9, to boost Lancashire's total from a meagre 117 for 7 to 182 for 9 after winning the toss. Newby then claimed the important wicket of Alex Gidman just as the Gloucestershire captain was threatening to rescue his side from a poor start.
The result puts Lancashire on 16 points in Group A, with two matches still to play, and meant they cannot be overtaken. It also eliminated Gloucestershire, who are on 11 points, with only one game left.
It looked good for the home side when their opponents collapsed from 63 for 1 to 117 for 7, thanks largely to a series of loose shots. But Newby came in to hit three fours and a six, sharing a stand of 37 for the ninth wicket with Stephen Parry, who made 12.
Left-arm spinner Ed Young was the pick of the Gloucestershire attack, with 2 for 25, but there were also three wickets for left-arm seamer David Payne.
Chapple contributed a useful 16 towards the end of the Lancashire innings and the 38-year-old then blew away Gloucestershire's top order, sending back Rob Nicol, Benny Howell and Dan Housego in taking 3 for 8 from four overs.
Ajmal Shahzad had already seen off Hamish Marshall and at 16 for 4 Gloucestershire were in disarray. But Alex Gidman looked in prime form as he counter-attacked with four boundaries in an over from Shahzad, including three from successive balls.
He was looking a real danger to Lancashire when Newby had him picked up at cover, having faced only 26 balls for his 36.
It was 75 for 6 when Ian Cockbain top-edged a sweep off Gary Keedy to be caught at deep square. But Will Gidman (32) and Fuller added 55 to give Gloucestershire hope before Gidman was stumped off the bowling of Steven Croft. Fuller almost turned the game around, but Chapple returned to remove Young and Jon Batty before Shahzad had Fuller caught behind to end the game.