It was his first show of real form for the entire season and he has been guilty of galloping in some of his recent runs which must have left even his most ardent fans worried they would never see the best of him again.
So trainers Greg and Nina Hope rolled the dice and sent him north to champion trainer Barry Purdon, who wasn't claiming too much credit for the win, as he only took over A G's White Socks on Monday night.
Purdon rang Maurice McKendry, who is not even one of his regular stable drivers, to partner A G's White Socks and McKendry admits he was surprised to get the call, let alone the win.
"I thought I'd be watching the series from the drivers' room, so I was happy to get on him, but he is a lovely big pacer," said McKendry.
While Cruz Bromac was still very good running second, the incredible form turnaround from A G's White Socks suggested there could be more twists and turns to come in this pacing series.
There was plenty to like about horses like Thefixer, Colt Thirty One, San Carlo and Ashley Locaz in their respective heats and there was an excuse for expensive failure Bling It On.
He over-raced badly in front in the A G's White Socks heat but was found to have been hitting the sulky wheel disks with his hooves so will need a cart adjustment for the second round on Tuesday night.
Upsets in trotting heats
The upsets started early in the trotting heats as Paramount King made the most of a perfect trail to trot a national 2200m mobile record in the opening heat.
The first surprise came when Dominion winner Habibi Inta was slow away from the mobile and got pushed back to last, launching starting the last 800m but peaking on his run in the straight.
But the winner was very good and thrilled co-trainer John Dickie, who has yet to win a trotting Inter Dominion in his storied career.
The second heat also had an early surprise when Marcoola was crossed at the start and then forced to race three back in the inner before Winterfell went on to win in the bravest style.
A former star 3-year-old Winterfell has been the problem child of the open class ranks in the past 12 months but he looked spot on last night holding out Marcoola, who was a solid but not totally convincing second.
The question mark horse out of the race was NZ Free-For-All winner Tough Monarch, who dropped out to last after leading.