While the bright lights and noise from the packed stands had an unsettling influence on his team-mates, the US-based Webby, making his Olympic debut, excelled in the conditions.
Riding at No 2 in the New Zealand line-up, Webby, originally a reserve, fashioned a strong round aboard Sitah, their only blemish coming at the eighth fence of 12, to incur just the four faults.
That left Webby, easily the best-placed of the Kiwi quartet in an equal share of 30th in a tightly-packed leaderboard.
Thirteen riders in the 77-strong field shared top-billing after jumping clear rounds within the optimum time of 88 seconds.
The most experienced of the New Zealanders, four-time Olympian Bruce Goodin, riding Yamato, could do no better than 66th after dropping three rails and incurring two time penalties.
It was disastrous night for Katie McVean and Sharn Wordley, both attending their first Olympics, in finishing 75th and 77th respectively.
"It was a hard night at the office and very disappointing for a couple of these guys that have put such a great effort into this campaign," New Zealand coach Greg Best said.
"To have things go the way they did tonight was a really tough start for them. The team competition is in two day's time and everybody starts on a clean slate so that's the way we've got to look at it from here."
It was an unhappy introduction for the promising McVean, on Forest, who faced automatic elimination after falling at the penultimate fence.
In the trailblazing role for the New Zealanders, McVean, 22, and her 16-year-old grey gelding made a promising start but the enormity of the occasion seemed to catch up with the combination as they progressed around the course.
Clear over the first four, dropped rails at the fifth, the second of the double at six and two at the treble had the newcomer struggling before a fall at the 11th had McVean tumbling out of the individual contest.
Full of jumping after a surprisingly quick recovery from colic surgery in April, Webby said his experienced dark bay mare had thrived under the lights and was buoyed by the enthusiastic crowd. Webby was a late replacement for Daniel Meech, who was forced to withdraw his injured horse Sorbas two days out from the competition.
Wordley could not repeat his excellent form of the last US season with his mount Rockville seemingly overwhelmed by the lights to the point of distraction to only clear three jumps cleanly.
"The bottom line is that we are lacking horse power," Best said.
"We have some truly world class riders on our team, the only thing they lack, and I think it was evidenced tonight, was a little bit of horsepower."
The second round of the individual competition and the team event takes place on Sunday.