Zara Phillips delivered a stunning performance in front of 50,000 people on her Olympics cross-country debut at Greenwich Park to keep Great Britain firmly in eventing medal contention.
The 31-year-old former world champion produced a clear round inside the time, completing a course that claimed its fair share of casualties.
Seven of the first 27 combinations fell and were eliminated, but Phillips kept supreme control all the way around a testing track that was very slippery in places.
Her team-mate Nicola Wilson also went clear inside the time aboard Opposition Buzz, while 51-year-old Mary King collected just 1.2 time penalties on Imperial Cavalier.
The British could not have hoped for better displays from their first three riders - and they still had former European champion Tina Cook and current world number one William Fox-Pitt to go.
Speaking after competing, Phillips said: "I am so happy. He is such a dude. He lost a front shoe, so he really stepped up. He was awesome - the course was very suitable for him."
Five combinations were clear inside the time as the competition entered its second half - Phillips, Wilson, Germany's Ingrid Klimke, Sweden's Sara Algotsson Ostholt and Australian Christopher Burton.
Phillips 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.
Earlier, Canadian rider Hawley Bennett-Awad required medical attention after falling at fence three, with her condition described by organisers as "stable" while she underwent further assessment in an on-course ambulance.
Belgian Carl Bouckaert fell at the same fence, while Japan's Takayuki Yumira also parted company with his horse Latina, which required the horse being treated.