Batting first, the all-conquering visitors mustered a daunting 239 for 8 from 36 overs after rain delayed the start by 25 minutes and Derbyshire's bowlers failed to deliver their full quota of 37 overs.
Brian Lara proved a disappointing failure with the bat but Neil Smith (56) and Roger Twose (74) came to the fore to ensure that Warwickshire did not under-achieve. Twose's final 58 came from only 26 deliveries as Warwickshire accelerated - all to no avail, rain washing out the rest of the day's play.
Nick Cook, the veteran spin bowler who had already caused Hampshire grief with the bat in the current Championship match at Southampton, took two wickets in his final over to help guide Northamptonshire to their six-run League victory.
Hampshire were chasing a target of 192 and had reached 170 with two overs remaining before Cook, who registered an unbeaten 43 in a frustrating last-wicket stand for the hosts on Saturday, had Paul Terry caught at long-on by Tony Penberthy for 95 and Kevan James caught going for another big hit.
Yorkshire slipped further out of contention when they suffered defeat at Durham. The Tykes struggled to 174 for 9 and the home side were on 165 for 4 after 31.4 overs when rain arrived to give them a comfortable win on faster scoring rate.
Yorkshire's defeat allowed Kent to jump over them into fourth place following their 50-run success over Gloucestershire at Cheltenham.
A hard-hitting unbeaten 72 by Adam Hollioake helped see Surrey to a comfortable six-wicket win over Sussex at The Oval. Andy Smith contributed an undefeated 32 as an unbroken 72-run fifth-wicket partnership took the hosts to 189 for 4 in reply to Sussex's 185 for 7.
Glamorgan defeated Somerset by five wickets with only six balls to spare in an exciting finish at Swansea in a match reduced to 24 overs a side. Somerset fielded superbly as the hosts chased 108 for victory, but David Hemp steadied things with what proved to be a match-winning 35.
Essex, the bottom club, ran into more trouble when they went down by seven wickets to Middlesex at Uxbridge. Phil Tufnell celebrated his imminent return to the Test arena by taking 2 for 25 from eight overs as Essex fell away dismally, a score of 135 presenting little difficulty to Desmond Haynes and Mike Roseberry.