Winterfell was so dicey in his trotting action Purdon had to let third place-getter Massive Metro head his horse before the home turn when the All Stars trotter still had more to offer.
Purdon admitted if he had not put the magic hands that helped him drive six prior Interdominions winners to work, the 5yr-old would have blown to pieces.
"I was very nervous. He just didn’t handle the corners, particularly the last corner. I just had to nurse him to keep him trotting.
"He was probably a neck behind Massive Metro on the home bend.
"I am sure if I had tried to go with Massive Metro he would have galloped."
Once balanced in the straight, Winterfell fought bravely to hold off a late dive from a wayward Majestic Man by half a neck.
The victory was Purdon’s eighth as a trainer and training partner Natalie Rasmussen’s fifth to confirm their status as Interdominion king and queen.
They added another Interdominion win just over an hour later when Ultimate Sniper won the pacing final on a night of total domination by the All Stars stable.
Winterfell, bred and raced by Trevor Casey, of Canterbury, disgraced himself when galloping in the Ashburton Trotters Flying Mile and the New Zealand Trotting Free-For-All before he set the Interdominions alight with two crushing heat wins and his hard-fought final victory.
"He is off the hook now," Purdon said.
"He is much happier this way round. That was the start of it, I think, and he just got more confident as the series went on."
Casey added the trotting victory to the pacing title Lazarus won him in 2017.
"To win an Interdominion final after I ran second 20 years ago [to Special Force], with Africa, to come back here and win it, it’s very special," Casey said.
The team behind runner-up Majestic Man was left wondering what could have been when the 5yr-old ran waywardly at the home turn, before launching a big finish when the race was effectively over.
Trainer Phil Williamson said his trotter hung out when keen to get a run.
However, his son, Brad, who drove the horse, was able to angle him into the passing lane.
Majestic Metro recovered well enough to reel in Massive Metro, who fought on for third after putting Winterfell under pressure on the home turn.
