Middleton (342-2) produced a stunning run chase as they beat Horsham (340-7) to make three wins out of three.
Michael Thornley (150) and Will Beer (100) were the stars for Horsham in their total with a partnership of 257.
But Sean Heather (144 not out), Jack Dawling (54) and a 62-ball 100 not out from Mahesh Rawat saw Middleton home in the 48th over.
Preston Nomads (257 all out) also made it three wins out of three as they beat Eastbourne (199 all out) by 58 runs.
Harrison Ward top-scored with 77 while James Hockley took 4-35. Ben Barter hit 54 for Eastbourne but it was Ward’s day as he completed a superb all round performance with 4-46.
Reigning champions Roffey also maintained their 100 per cent record beating Three Bridges.
East Grinstead (254-4) enjoyed a good run chase to beat Cuckfield (250-9). Overseas Harry Nielsen (88) and Tom Weston (79) starred for Cuckfield while Lewis and Bradley Hatchett took three wickets apiece.
Will Adkin (80), Tom Haynes (52) and Leo Cammish (71 not out) lead EG to victory.
Bryce Hounsome hit 112 as Brighton and Hove (271-8) beat Mayfield (218 all out). Hounsome was supported by Matt Machan, who hit 59 from 38 balls.
Ashley Wright (66) and Will Sheffield (52 not out) batted well for Mayfield while Machan took 4-35.
St James’ Montefiore and Billingshurst lead Division 2 as they both made it three wins out of three.
St James’s (137-0) cruised to a 10-wicket win over Goring-by-Sea (132 all out). Jordan Shaw, Michael Murray and Henry Cope all took three wickets before Hector Loughton (88 not out from 53 balls) saw St James home in 14.4 overs.
Billingshurst (99-7) beat Ifield (95 all out) in a low-scoring affair. Hurst skipper Ben Williams took 6-22.
Haywards Heath (184-5) beat Burgess Hill (182 all out) in the Mid Sussex derby while Bognor (168 all out) beat Lindfield (130 all out) with Roy Kaia, Joe Ashmore and Mikey Harris taking three wickets apiece for Bognor.
Hastings and St Leonard’s (163-5) beat Chichester Priory Park (160 all out) by five wickets.
Division 3 West: Broadwater 174 all out (42.2) lost to Pagham 214-8; Littlehampton, Clapham & Patching 247-9 beat Stirlands 166-9; Roffey 2nd XI 304-7 beat Findon 90 all out; Steyning 214-2 beat Worthing 213-9; West Chiltington & Thakeham 131 all out lost to Ansty CC171 all out. Highlights: Sachin Naik 97 and Fred Bridges 4-12 for Roffey; Isaac Tidley (77) and Ben Buckley (64) 161 partnership for Steyning.
Division 3 East: Crawley Eagles 186-9 lost to Seaford 189-7; Hastings & St Leonards Priory 2nd XI 218-4 beat Rottingdean 217-2; Rye 88 all out lost to Brighton & Hove CC - 2nd XI 210-7; Portslade 208-9 beat Bexhill 193 all out; Preston Nomads 2nd XI 99-5 beat Eastbourne 2nd XI 98 all out. Highlights: Paul Glover 50 not out and 4-20 for Portslade; Brad Smith 90 not out fo Hastings; Connor Bettsworth 113, James Bergin 74 for Rottingdean.
Other highlights: Sean Dobbs 102 not out from 68 balls for Chichester Priory Park 2nd XI; Toby Pierce 103 not out for St Peter’s.