Sussex drubbed Kent to claim their place in the Clydesdale Bank 40 semi-final, where they will meet t20 winners Hampshire.
Starting the day in second place to Kent in their group, Sussex prospered as an unbeaten century by Luke Wright and 78 not out from Matt Prior helped them chase down 211 for the loss of one wicket.
All was not lost for Kent at the conclusion but, once Warwickshire's win at Yorkshire was confirmed, their chances of being the best losers disappeared. Warwickshire's reward for climbing from third in their group to take the best runner-up place is a trip to Lancashire, who were impressive until the rain came.
Opener Tom Smith smashed one of the quickest one-day centuries in history before a rain-curtailed fixture against Worcestershire was abandoned at New Road. The 26-year-old all-rounder (106) made a triumphant return from a five-week injury lay-off by racing to three figures from 44 balls with eight fours and 10 sixes.
Warwickshire set up the tie against Lancashire with a 55-run Duckworth-Lewis victory over Yorkshire at Scarborough. In a Group C game reduced to 29 overs by rain, Yorkshire found themselves chasing a revised target of 214 after Tim Ambrose had led the Warwickshire charge to 211 for six with an unbeaten 87.
Yorkshire managed 158 in deep gloom, with Warwickshire beneficiary Neil Carter (four for 16) coming to the fore on his first one-day appearance of the season to snap up the first three wickets at a cost of only eight runs.
For their part, Hampshire clinched an away semi-final when Somerset versus Surrey was declared a no result shortly before their game with hosts Durham went the same way. Somerset and Surrey had both harboured hopes of taking a best-placed second but were denied when their match at Taunton was abandoned after just 27 balls were bowled.
Gloucestershire's young bowler Liam Norwell claimed competition best figures of six for 52 before their game against Leicestershire was abandoned as a draw at Grace Road.
Nottinghamshire and Glamorgan shared the points as rain also forced their match to be abandoned with no result at Trent Bridge. Derbyshire and Northamptonshire were others to thwarted by rain, with the elements ending their game at the halfway stage after the visitors had scored 232 for eight.
A century from Dawid Malan acted as the catalyst for a Middlesex victory by 54 runs under the Duckworth/Lewis method against Essex at Lord's. Malan deployed controlled and clean-hitting aggression in his innings of 134 from 108 deliveries out of a total of 288 all out.