Spearman-Burn, 27, birdied the first hole to take a lead he never surrendered in a sumptuous display of precision golf to take out the match 4 and 2.
"I didn't have much luck or get any momentum going but that's golf. If you don't win, you learn," Campbell said.
"I am really proud of what I have done and made a few people look and see what I can actually do.
"I am pretty happy with the way I played this week. It is pretty cool to know you can actually compete with top guys in New Zealand like Luke Toomey and all those guys who have just come back from the Asian Amateur.
Campbell went to Wellington boosted by being named in Bay of Plenty senior team to contest the Men's Toro Interprovincials in New Plymouth later next month.
"The previous tournaments leading up to this I hadn't been playing that good but I did have a couple of good rounds and managed to get the putter rolling this week.
"I just went out there and tried to play the course and had some fun with my playing partners. It all sort of just fell into place.
"I wasn't expecting to go out there and win the qualifying but somehow it just happened. I just stuck to the same game plan all week of just going out there and having fun.
"I felt like being the underdog all week and it just made me play all that much better. Just going out there with a relaxed attitude helped me play well this week."
Campbell is a noted big hitter and enjoyed the extra length of the Royal Wellington course.
"Yeah it suited me. It's quite long and with soft conditions it helped my ball stop on the fairways a bit more. It gave me a few more chances to hit it closer and make a few more putts on the greens so it definitely helped me."
It would be understandable if Campbell was nervous taking on the illustrious company he was with but apart from some typical first-tee nerves he said he felt relaxed throughout the tournament.
He appreciated having so much support from the Bay of Plenty golfing community and on course from his family and sister Alanna, who qualified fourth but was knocked out of the women's tournament in matchplay rounds on Friday.