Champions Preston Nomads are virtually home and dry in their bid to retain the Premier title after seeing off the challenge of Horsham.
The hosts set a challenging 251-7 as John Burroughs (78), Tom Haines (57) and Will Williams (50) led the way.
But Nomads set about their task with relish as Patrick Spencer (104) and Joe Gatting (94no) swept them to a five-wicket win.
The following day Nomads more or less put the seal on the title as they became the first team this season to beat the youngsters of the Sussex Development XI.
Conor Golding top scored with 46 as the Sussex side were bowled out for 150 as Spencer swopped bat for ball with 4-28.
Gatting then went on a personal crusade with 84 not out to complete an eight-wicket victory in the 39th over.
No such joy for enigmatic Cuckfield the previous day, however, as they probably regretted their decision to bat first on a home track likely to give the bowlers help early on.
East Grinstead bowled superbly, offering little width and holding a good length with relentless patience.
As a result, none of the main batsmen settled in for too long and only a last wicket stand of 31 between Harry Clark (33) and Kurtis Browning (12no) took the hosts to some respectabilty at 149.
It was never going to be enough, however, and EG completed a seven-wicket win in the 33rd over as Will Adkin (45no) and Tom Haynes (24no) figured in an unbroken stand of 72.
It was a bad day for St James’s in Division 2 as they became only the second team to lose to bottom club Pulborough this season.
There were five ducks as Jonathan Bennett took 7-35 to send the visitors crashing to 68 all out and set up an eight-wicket win.
Haywards Heath II continue to struggle as Eastbourne made 266-1 and then met resistance from only Dan Woodfield (74).