Feeling so nervous he was barely able to hold his putter on the final green at Royal Birkdale, the popular Kiwi still managed to play the "perfect" 18th hole, birdieing the brute with a 12-foot putt to win the title by one shot from American Cameron Young in Sunday's thrilling finale.
Behind the 39-year-old were a host of tales of near-misses, including Australia's Lucas Herbert, who was still hanging tough in the hunt for the crown at the famous Lancashire links as he teed off at 17, still requiring two birdies to match clubhouse leader Young on nine-under.
But an untidy penultimate hole, where the 30-year-old drove into the bushes, got bunkered with his third shot and ended up with a bogey six, followed by a par at the last, ensured Herbert could only finish on six-under, tied for sixth four shots behind the winner.
But up ahead, Fox, son of World Cup-winning All Black flyhalf Grant Fox, proved unbreakable in his mentality, looking, as he had all afternoon, like the one golfer out there ready to dare to attack for glory.
Fox, who became only the second New Zealander ever to lift the Jug after Bob Charles 63 years earlier, had endured bad luck during the round, coming up against a bunker lip on 15 and just trickling into a fairway sand trap after a fine drive on 17, but he refused to be daunted.
After missing a 10-footer on 17 to take the lead, he drove off on 18 tied with Young, who had earlier given all the field a severe target to match after a 64, the best round of the entire day.
Sam Burns was also in a position to match Young's total if he could hole his birdie putt at the last, but it slid by for the overnight leader to finish third on eight under.
But Fox played a glorious approach on the final hole, the popular Aucklander, who never wastes any time on the course, then quickly knuckling down to sink the winning putt for a 68 and a winning total of 10-under, before pumping his arms in joy.
"With me, it's always been 'see a shot, hit a shot'. As soon as I start thinking about it too much, then some bad stuff creeps in," smiled Fox.
"On the last, I hit two perfect shots. I'm not sure how I hit the putt. My hands were all over the place; I was just trying to get it towards the hole somewhere. It's surreal that it went in. Yeah, 'Champion Golfer of the Year' has a pretty good ring to it."
His wife and two children were in Florida. "I spoke to my kids last night, and they said, 'bring back a trophy'. I think this is a pretty cool one to bring back for them!"
Ultimately, as the sea breezes kicked up to make Birkdale a real test on the final day with Fox being one of only three players in the final 12 groups to shoot under par, all his main rivals were far too error-prone.
That included Herbert, who like Fox, had earlier in the week recorded a record-equalling all-time low round in a men's major championship, with a landmark eight-under 62. His four bogeys on Sunday eventually sank him.
"I can't be too upset," shrugged the Victorian, who shot a final-round 71 but just missed out on the top-five finish which would have earned him a place in all the majors next season.
"A lot of positives to take. It's my best finish in a major. I genuinely contended. I was up around the lead for the last 45 holes. There's a lot to take away from that. I've learned so much this week."
World No.1 Scottie Scheffler (67) finished tied for fourth on seven under, alongside local hero Tommy Fleetwood (68), while South African Casey Jarvis (66) and Korean Si Woo Kim (72) were alongside Herbert in fourth.
Evergreen Australian Adam Scott, at the age of 46 and in his 101st consecutive major, earned his seventh top-10 finish in an Open, with a final round 66 earning him joint-ninth position on five under.
Like everyone else, though, Herbert was delighted for Fox, who's one of the most popular performers in golf. "His manager and my caddie are really close. Yeah, the Aussies and the Kiwis tend to stick together out there, familiar breed," smiled Herbert.
