On lap three, a group of five including Cheatley, Adrian Pettit, Brent Bismark, Jason Sturzaker and Duncan Appleton went clear on the state highway leg of the course and, with Cheatley and Bismark driving the bunch, they continued to increase the margin over their opposition.
The lead group entered the Francis Rd finishing straight with a handy margin over the rest of the field
In the rush to the line, Cheatley produced his usual sharp sprint to cross first. Jason Sturzaker was close up in second, with Duncan Appleton right there in third, Pettit fourth and Bismark fifth.
Heading in the next bunch was Jason Bardell, who rode well to claim sixth over the line.
Meanwhile, after a good steady race, Darby finished close up in the second main bunch and once times were corrected, his effort was sufficient to see him awarded the race win.
Darby has only been racing for a year and has shown sharp improvement in recent weeks.
His effort on Saturday is clearly his best at this level to date and is perhaps a sign that he has a good future in the sport.
Bardell may have been sixth home, but on handicap he secured the official nod for second and Shaun Tucker put in another strong ride, placing third on corrected time.
The small field of B-graders raced over four laps 36km of the same circuit under the same conditions.
Once the handicapper's calculations were complete, Dean Blackwell was awarded the win, the consistent Murray McDonald second and Craig Bright third.
Tamara Ross and Paul Darby were fourth and fifth respectively.
Comeback rider Stephen Gibson out-rode his handicap to win the two-lap, 18km C-grade race.
He has recently returned to Wanganui to work for an accounting firm after completing his university studies and was back racing again for the first time in five years.
The ever present Debbie Cain was credited with second place, with another hardy performer, Julie Weir, taking third.
Results
A-grade: 1. Boaz Darby; 2. Jason Bardell; 3. Shaun Tucker. Fastest time: Bevan Cheatley.
B-grade: 1. Dean Blackwell; 2. Murray McDonald; 3. Craig Bright.
C-grade: 1. Stephen Gibson; 2. Debbie Cain; 3. Julie Weir.