Adam Gosney showed glimpses of his strength despite being short of race condition and Steve Cowan, Mike Wright, Darcy Forrester, Martin Hogan and Brian Scrimshaw were regular contributors.
By the halfway mark the field was still largely intact, but on the small rise shortly after the turn five riders were dropped, who despite their best efforts were unable to reconnect with the front bunch.
On the return leg, Bismark and Johnstone took turns to attack off the front, though neither gained a decisive break.
The other frontrunners continued to chime in regularly as McNeil started to appear on the front, as did Dan Richards.
At Sparrow cliff, Cowan streaked out to a lead of over 100m and momentarily looked like he might ride away.
However, Bismark and company were having none of that and brought him to heel at the small bridge, with 1km to travel.
The finishing straight saw the usual jockeying for position as McNeil swung to the outside in what proved to be a great piece of timing and unleashed his sprint early.
Approaching the line, Bismark was mowing him down, but McNeil had just enough in reserve to hold him off and take the win.
McNeil is a regular visitor to Wanganui and, although he has previously tasted success here, Saturday's victory was up with his best performances.
Bismark's second placing was well earned, as was Brian Scrimshaw's third having been in the thick of the action throughout.
Forrester competitive as ever in this type of race was close up in fourth, narrowly ahead of Richards, with veteran Allan Luff turning in a sound performance to claim sixth.
The seven B-graders raced over the same course and distance with Craig Bright, Carl Rusden and Pat Carroll in particular looking strong.
Stu Bruce and Graham Jefferies blew out at halfway, leaving a lead group comprised of Bright, Rusden and Carroll with Geoff Springer and Rod Trott for company.
Nearing the finish, Bright decided on a long-range sprint and had a decent break inside the final 200m.
Charging at him late, Rusden only just failed to peg him back. Bright took the win, though both riders were credited with the same time.
Carroll was just 2 seconds back in third, with Springer nailing down fourth ahead of Trott before gaps to Bruce and Jefferies respectively.
A field of 10 contested the 19km out and back C-grade race to River Rd.
It was Alastair Ross who sprinted out of the pack to score.
Ross is a regular golfer, but a broken finger is preventing him playing at present and he is keeping fit by cycling.
His injury clearly has not hampered him in that regard and he showed he had learned from last week's experience, racing more conservatively and saving himself for a winning final burst.
Alison Richards was only just mown down short of the line and showed she is back, better than ever after a long break.
Dean Blackwell again put in a handy race for third, with the returning Mike Donoghue battling well for fourth ahead of Julie Weir's fifth and Dennis Squires in sixth.
Results:
A Grade: R McNeil (fastest time 53.46) 1, B Bismark 2, B Scrimshaw 3.
B Grade: C Bright (fastest time 1.00.24) 1, C Rusden 2, P Carroll 3.
C Grade: A Ross (fastest time 35.01) 1, A Richards 2, D Blackwell 3.
