The trotter gave McIlwrick his 39th win of the 2016-2017 harness racing season on its final day yesterday, giving him a comfortable margin over Matt Anderson whose tally finished on 25 wins.
Sealing victory in the premiership on a Phil Williamson-trained trotter meant a lot to McIlwrick, who has had a close association with the Williamson family throughout his career.
''It's good to win the premiership, but it is special to win it on one of the Williamsons' horses,'' he said.
Yesterday's meeting was McIlwrick's last before he heads into the open driving ranks.
He confirmed his premiership win on the back of his New Zealand Junior Drivers Championship title earlier this month and is well-placed to make that next step.
''I'm not a junior next year, so we are all done,'' he said.
''I couldn't have finished it in a better fashion. It's been a pretty special last month and I have really enjoyed it.''
McIlwrick is in esteemed company as a 2017-18 season premiership winner.
Mark Purdon and Natalie Rasmussen, of All Stars Stables at Rolleston, won the trainers' title with their 110 wins, while Cantabrian Dexter Dunn won and set a record in the drivers' premiership with his 228 wins.
Freshman pacer Admiral's win could prove to be a case of here one day, gone the next.
The Gavin Smith-trained 2yr-old justified his $1.60 tote favouritism with a comfortable win in his second career start yesterday.
He has been the subject of good interest from Australia, Smith said.
Up to five potential buyers had shown interest in the horse prior to yesterday's race. He was shuffled back to last and then hit the line strongly in behind Tara Tutaia at Rangiora, earlier this month, and they wanted to see him race again, Smith said.
Admiral raced handier to the pace at Oamaru yesterday and won easily, meaning the sale of the horse, raced by northern racing photographer Trish Dunell and her son, Cameron Mackie, was likely to be completed soon.
''He's a nice horse. He's got a lot of high speed,'' Smith said.
''I'm sure wherever he ends up he will go a really good job.''
Eden Creek added another winner to the famous trotting breed she descends from with her maiden win yesterday.
The Len Mosely-trained-and-owned 4yr-old outsprinted the race favourite, Jerry Garcia, to win the opening event on the Oamaru programme.
Eden Creek is the first foal from Becky, whose grand-dam, Kahlum, produced 56-win
trotter Lyell Creek.
Becky has also left a 2yr-old by Monkey Bones for Mosely.
In yesterday's feature trot, All Lit Up notched an impressive win that even the great Lyell Creek would have been proud of.
The 8yr-old Sundon gelding did plenty of work racing outside the leader, Playboy's Brother, but that did not stop him charging away to a three-length victory for driver Justin Smith, who trains the mare with his mother, Lynn.
Mistacullect won the feature pace for Temuka trainer Brent White and driver Craig Thornley.
In the race prior, Speedy Mach maintained his record of never finishing out of a top-two position on the Oamaru track with his two-length win for trainer Brad Mowbray and driver Matthew Williamson.
