Suffolk's Ian Graham led the charge on a day dominated by ECB 38-County Cup centurions.
Graham blitzed the Hertfordshire bowling for a magnificent 130 off only 87 balls (24 fours and two sixes) as his side hurried past a 234 target for the loss of four wickets in the 36th over.
Suffolk seamer Gary Kirk included a hat-trick in his figures of five for 27 as Hertfordshire were limited to 233 for nine - his victims being Owen Dawkins, Steve Andrew and Karl Stewart.
Stuart Airey, son of former Lincolnshire player Jim, also performed a hat-trick for the Nottinghamshire Board XI against Lincolnshire, but not before the Minor Counties side had scaled 300.
Their final total of 324 for five was their best ever in the competition, with Steve Plumb (130) and Jason Harrison (82) sharing an opening stand of 229 in 42 overs. Mark Saxelby matched Plumb's efforts to also score 130 but Nottinghamshire fell way short on 216 for six.
Ex-Gloucestershire batsman Bobby Dawson hit 127 for Devon as they saw off peninsular rivals Cornwall by 45 runs at St. Just while Staffordshire skipper Steve Dean piloted his side home against the Derbyshire Board XI at Heanor Town with an unbeaten 121 off 118 balls.
The Essex Board were the highest scorers of the day, their 361 for three against Huntingdonshire at Chelmsford the third highest total in the history of the one-day event. At the other end of the scale, Cambridgeshire slumped to just 77 all out against Norfolk, their lowest ever KO Cup score.
In the championship, former Middlesex and England Test spinner John Emburey helped himself to seven for 74 as Wiltshire fell short of any batting rewards on the opening day of their derby with Berkshire at Warminster.
Having dismissed Berkshire for 170 inside 50 overs - Jason Searle taking five for 47 - the early-season Western Division leaders fell away from 74 without loss to 166 for nine off 60 overs, missing out on a batting point by just one run on 149 for seven off 50.
Graeme Ion (59 not out) and Ollie Clayson (74 not out), two of the championship's young guns, scored unbeaten half-centuries for Cumberland and Bedfordshire respectively at Bedford Town - Cumberland skipper Simon Dutton also clubbing 59 off 51 balls - while Phil Evans, son of ex-Oxfordshire off-spinner Rupert Evans, took his first championship wicket against Wales at Banbury.
Minor Counties Championship
Bedford Town: Cumberland 278-5 (DJ Pearson 76, G Ion 59 not, SM Dutton 59) & 9-1 Beds 227-3 (OJ Clayson 74 not, AR Roberts 54 not)
Banbury CC: Oxon 229-5 (BJ Thompson 73, KR Mustow 68) & 37-3 Wales 153 (GS Peddy 5-36)
Warminster: Berks 170 (JP Searle 5-47) & 24-0 Wilts 166-9 (JE Emburey 7-74)
Weymouth: Dorset 176-7 Shrops 237-7 (JBR Jones 81, JV Anders 53, GR Treagus 4-89)
ECB 38-County Cup
St Just: Devon 258-3 (RI Dawson 127, MJ Wood 73) Cornwall 213 (GM Thomas 91, I Gompertz 4-26) Devon won by 45 runs
Hertford: Herts 233-9 (DM Ward 69, MA Everett 52, GM Kirk 5-27 inc. hat-trick) Suffolk 235-4 (ID Graham 130) Suffolk won by 6 wickets
Chelmsford: Essex 361-3 (N Carlier 152, GW Ecclestone 89, A Hibbert 78) Hunts 187-5 Essex won by 174 runs
Halesowen: Worcs 199-8 (J Tandy 90 not) Hereford 200-1 (R Nagra 90 not, CW Boroughs 68 not) Hereford won by 9 wickets
Raunds: Northants CB 212-8 (DJ Capel 99, L Pollard 5-33) Leics CB 215-3 (M Sutliff 83 not, L Reeves 57 not) Leics won by 7 wickets
Wisbech: Norfolk 245-8 (NJ Llong 90, A Akhtar 4-19) Cambs 77 (SC Goldsmith 4-24) Norfolk won by 168 runs
Heanor Town: Derbys CB 257-6 (P Davies 62, J Benstead 57) Staffs 258-3 (SJ Dean 121 not, JF Jervis 58) Staffs won by 7 wickets
Boots, Nottingham: Lincs 324-5 (SG Plumb 130, JC Harrison 82) Notts CB 216-6 (M Saxelby 130) Lincs won by 108 runs
Jesmond: Yorks CB 211-8 (P Carroll 68) Northumberland 212-3 (B Parker 90 not) Northumberland won by 7 wickets