"Obviously I'm thrilled, I've played really well all three days and I finally got something going on the last five holes."
Fox was in danger of missing the cut, sitting at one-over for the tournament approaching the par-5 14th hole, but he pulled out a moment of magic which turned his fortunes around, hitting a four-iron to three-inches and tapping in for eagle.
"14 kickstarted everything really, I played pretty solid up to that point without anything dropping. I had 248 to the flag, I was just trying to land it about 10 short of the green and run it up. It was a full four iron and I hit it perfect, the exact shot I wanted to hit. It ended up three inches away and I found out afterwards it had a really good chance of going in.
"To play really solidly after that and make it comfortably in the end was awesome."
Fox admitted to some nerves playing in the biggest tournament of his career.
"I was definitely nervous out there but it was nice to see some putts go in and hit some good shots when it really mattered. That's why we play sport in the end - you have to love the pressure."
Now, Fox is leaping at the chance to experience the rare environment of the weekend at a major championship.
"I've got nothing to lose. I get to play the weekend at my first major and soak it all up and hopefully build some experience for the next time."
"There should be quite a lot of people out, it should be the full experience of a major championship.
Fellow Kiwi Danny Lee's fate was already sealed on Saturday (NZ time) after he carded a two-over 74 in the second round, finishing three off the cut at three-over par.
The second round of the British Open finished nearly 39 hours after it began.
Play was suspended more than three hours on Friday because of heavy rain, and then halted for nearly 10 1/2 hours on Saturday by high winds.
The third round is now set for Sunday (Monday NZT), followed by the first Monday(Tuesday) finish at the Open since 1988.
American Dustin Johnson is the 36-hole leader with a 10-under 134, one shot ahead of England's Danny Willett, and two ahead of Scotland's Paul Lawrie, the 1999 Open champion.
Jordan Spieth is still in the mix after winning the Masters and the U.S. Open. Despite a shaky putter, he's within five shots of the top spot.