Steve Cowan was also putting in some decent work, as were Lewis Bunker, Paul Forrest and Rob Chamberlain.
On the ascent up the Montgomery Rd climb for the final lap, Scrimshaw launched a strong attack, and keeping the pressure on up the main road he had a break of over 200m for the turn into Rapanui Rd.
Just when it looked like Scrimshaw's bold move might pay off, a desperate chase spearheaded by Groves saw the bunch reel him in shortly before the turn onto the Francis Rd finishing straight.
In the final rush to the line, Sturzaker had too much zip for his rivals, narrowly heading off Cheatley in second with Cowan right on their wheels in third place. Darby nailed down fourth with Stanton close up in fifth spot, with his sound effort sufficient to see him awarded the win.
Bunker was next in and Forrest was seventh, securing the official second placing on corrected time from Chamberlain, who was right behind Forrest at the line.
In the keenly contested 36km B-grade race over four laps, Stephen Brandon ground out a nine-second win over a gallant Wayne McGrail, with comeback rider Catherine McMurray close behind in third.
Rob Manson did well for fourth, with Laurence Sunde fifth and Laurika Hazlehurst rounding out the top half dozen.
Five C-graders raced over two laps in an 18km circuit and it was the B-grade winner's namesake club sponsor Steve Brandon who scored a five second win over the experienced Steve Carle.
Youthful Damien Hussey was third, with Ian Steven and Craig Whittaker home fourth and fifth respectively.
Results
A-Grade: 1 Richard Stanton; 2 Paul Forrest; 3 Rob Chamberlain. Line honours: Jason Sturzaker (fastest time 1:14.00).
B Grade: 1 Stephen Brandon (fastest time 1:08.00); 2 Wayne McGrail; 3 Catherine McMurray.
C Grade: 1 Steve Brandon (fastest time 40.27); 2 Steve Carle; 3 Damian Hussey.