But seven of the first 27 combinations fell on a course that appeared to be very slippery in places and challenging in terms of its fences.
Canadian rider Hawley Bennett-Awad required medical attention after falling at fence three, Belgian Carl Bouckaert fell at the same fence, while Japan's Takayuki Yumira also parted company with his mount Latina.
Wilson and Opposition Buzz gave the Host Nation a flying start. The combination is regarded among the world's leading cross-country pairings, and they lived up to that billing.
The world and European team gold medallists delivered a brilliant round, finishing almost 12 seconds inside the time allowed of 10 minutes, three seconds.
An elated Wilson remained on her dressage score of 51.70 penalties.
He was just unreal, what a fantastic horse. This is his favourite stage by far.Nicola Wilson
She said: 'He was just unreal, what a fantastic horse. This is his favourite stage by far. When he gets to go cross-country day it's like all his birthdays and Christmases have come at once.'
Australian Christopher Burton went clear inside the time by a remarkable 17 seconds. He breezed around the 5,728-metre course on HP Leilani.
It strengthened Australia's position in the Team competition after they held the silver medal place overnight.
King, utilising all her experience, kept concentration and completed the course with just 1.2 time penalties, taking her overall score to 42.10 and into the lead ahead of Burton.
The third British team member, Zara Phillips, attacked the course with confidence from the start on her Olympic debut.
Despite her horse High Kingdom's relative inexperience, they relished the challenge and became the fourth combination to go clear inside the time, after Burton, Wilson and Germany's Ingrid Klimke.
The Queen's granddaughter punched the air as she went through the finish to an ecstatic reception from an adoring crowd as she finished on her dressage score of 46.10.