Rocky Flintoff made his first Lancashire century in a One Day Cup thrashing of Somerset - and will now meet Ben Stokes and Durham in the quarter-finals.
The 18-year-old son of former England all-rounder Andrew Flintoff brought up his maiden ton in 65 balls before finishing on 123 from 76 deliveries at Taunton as the visitors posted a new highest List A score of 443-6.
The Lancashire batter, who had previously made a hundred for the England Lions, smashed eight fours and four sixes on his way to his milestone moment.
Somerset later subsided to 269 all out in 39.2 overs, with Lancashire skipper George Balderson and Tom Aspinwall taking four wickets each as they coasted to a 174-run victory.
Lancashire will have home advantage in Friday's quarter-final after Durham lost by 77 runs at Worcestershire and finished third in Group B.
Stokes suffered some heavy punishment as his nine overs went for 61 runs, with one wicket as reward, and the former England captain was dismissed for one as Durham were all out for 214.
Yorkshire will host Nottinghamshire in the other quarter-final on Friday after finishing Group B runners-up.
Ben Coad (3-22) and Dom Bess (3-32) shone with the ball as Essex were dismissed cheaply for 151, and Will Bennison (60) and James Wharton (51 not out) helped Yorkshire complete a seven-wicket win.
Nottinghamshire qualified with a six-wicket win, overhauling Surrey's 298 with 13 balls to spare as George Munsey made 138 from 132 balls.
Leicestershire, who did not play on Tuesday, and Middlesex go straight into the semi-finals after topping their respective groups.
Middlesex wrapped up Group B with a comfortable 92-run win over Sussex. Joe Cracknell (128) and Nathan Fernandes (92) laid the platform for Middlesex's 354-8 with a third-wicket partnership of 202.
There were also wins for Derbyshire, Gloucestershire and Warwickshire.
