Charlotte Dujardin continued her remarkable rise to the top of world dressage today by putting Great Britain in team gold medal position and smashing an Olympic record.
The 26-year-old's breathtaking Olympic debut with Valegro gained a standing ovation from a capacity 23,000 crowd at Greenwich Park.
Their grand prix score of 83.66% was more than four percentage points better than the previous Olympic best of Germany's Kristina Sprehe that stood for just two hours.
The team competition resumes and concludes next Tuesday with the grand prix special test - Enfield-born Dujardin is world record holder in that discipline - with Britain having never previously won an Olympic dressage medal.
Their current team score of 79.40% - the average mark of all three riders Dujardin, Carl Hester and Laura Bechtolsheimer - is 0.56% above Germany, with Holland (76.80%) third.
Dujardin's score was the best over two days of competition, with Dutch star Adelinde Cornelissen in second, Germany's Helen Langehanenberg third, Hester fifth and Bechtolsheimer seventh.
Barely 20 months ago, Gloucestershire-based Dujardin had never ridden a competitive grand prix test, but today's performance has increased the prospect of double Olympic gold.
The individual competition - freestyle to music - takes place next Thursday and closes the Olympic equestrian schedule.
When Dujardin performed her Olympic freestyle routine during an event at Hartpury in Gloucestershire last month she set a new British record of 90.65%.
"It is an amazing opportunity to ride here, and I really wanted to enjoy it," said Dujardin, who was only 0.42% short of equalling Edward Gal's world grand prix record with Totilas.
"I would hate to have gone in there, put too much pressure on myself and made mistakes.
"I just wanted to go in and do what I do normally and have fun. Having the crowd behind me like that was amazing.
"I was hoping for an 80% score, so to come to the Olympics and smash that is a little bit crazy, but I had such fun.
"It was such a buzz, I can't tell you. I just wanted to get in there and do my piece."
Dujardin's horse is part-owned by her training mentor and team-mate Hester, and he watched from the stands as she produced a test that left no-one in any doubt about the combination's quality.
"Valegro was just unbelievable. He is only 10 and we only started grand prix last year," she added.
"He knows when he gets in there what he has got to do. Touch wood, he never lets me down. There was not a single moment of worry.
"I just enjoyed it from start to finish, and then when you stop and you have the crowd responding like that, it's just magic.
"I wanted to pull out a score for everybody, and I am wearing my lucky breeches - the ones I broke the world record in - so maybe they helped."
If Britain land team gold in four days' time, it will be the first time since 1972 that Germany has not won the Olympic title.
Earlier in the day, Britain's Richard Davison produced a strong performance to secure grand prix special qualification.
Davison, at 56 the oldest member of Team GB at London 2012, is competing in the Games as an individual.
The top 11 individual scores, plus all three members of the leading seven teams after today, go forward to the grand prix special stage.
And Davison showed all his experience aboard 13-year-old Artemis, gaining a grand prix score of 72.81% to stand 18th overall.
It was not easy, though, as a torrential downpour during the final stages of his warm-up tested horse and rider.
"Boy, did I work hard," said Staffordshire-based Davison, who is competing in his fourth Olympics and is a former European team medal winner.
"The rain came during the last 10 minutes of our warm-up time, and Artemis got scared and jumpy, so the last 10 minutes before I went into the arena was not what I had been dreaming about.
"In the arena I just knew I had to keep him busy because he was scared. It was like taking a child to school on its first day.
"The beginning of the test was tricky, but as time went on he started to come back to me."