Pietersen returns to form
Kevin Pietersen returned to form with an impressive 116 - his first hundred in any format for 18 months - as Surrey played out a thrilling Clydesdale Bank 40 tie with Sussex.
Pietersen, who is finishing the season by playing four games in a two-week loan spell at Surrey after he was left out of England's one-day squad, made 116 in front of a crowd of around 5,000 at Hove.
It was Pietersen's first domestic one-day hundred for seven years and he never looked in any trouble even though the Sussex attack contained three players with Test experience.
Surrey made 240 all out, with Sussex finishing on the same total for the loss of eight wickets.
There was also an unbeaten 101 from Alastair Cook as Essex eased to a seven-wicket victory over Yorkshire at Headingley Carnegie.
Yorkshire were guaranteed a home semi-final tie at Scarborough next Saturday regardless of the result and they have been drawn against Warwickshire, while Essex's win took them into the last four where they will face Somerset.
Cook’s knock saw Essex past Yorkshire’s 209 for eight with three wickets down and 3.3 overs left.
Peter Trego's career-best 147 and a blistering 90 not out from Jos Buttler saw Somerset to a 249-run thrashing of Glamorgan in their final Group A match at Taunton.
The home side's total of 368 for four after winning the toss was their highest ever 40-over score. Trego hit 19 fours and five sixes, while Buttler faced only 33 balls and smashed eight fours and seven sixes.
David Harrison shipped 100 runs from his eight overs.
Imran Tahir claimed 4-27 as Warwickshire held on to top spot in Group C with a seven-wicket victory over Nottinghamshire at Edgbaston, cementing their semi-final place.
Tahir and co kept Nottinghamshire to 192, a target comfortably overhauled by England duo Jonathan Trott and Ian Bell, who made 84 not out and 50 respectively.
Durham's Neil Killeen was denied victory in his final match before retirement as Kent defended a modest total of 144 to win at Emirates Durham ICG.
Killeen, bowing out after 16 years, took 3-24 as the visitors were bowled out in the final over of the first innings but their bowlers ensured they had plenty as they secured a 31-run win.
Owais Shah marked his final one-day appearance for Middlesex with an unbeaten half-century that helped steer them to a comfortable seven-wicket win over Derbyshire at Lord's.
Shah made 58 and Scott Newman added 90 as the hosts made light work of a 196-run chase.
A maiden half-century for Luke Procter carried Lancashire to an entertaining four-wicket win over Worcestershire at Liverpool.
Procter shared a crucial sixth-wicket partnership of 62 with debutant Jordan Clark as they chased down 259.
Alexei Kervezee made 111 in a losing cause.
James Franklin and Chris Taylor both hit centuries as Gloucestershire saw off Northamptonshire in an 82-run win at Wantage Road, but it was not enough to earn the visitors a last-four spot.
Harry Gurney claimed career-best figures of 5-24 as Leicestershire closed their campaign with a 14-run victory over Hampshire at Grace Road - their first win at home in the competition since the opening match of the season.
The Foxes made 241 for three, with Gurney leading the defence.