Great Britain's Richard Davison produced a strong performance to put himself firmly on course for grand prix special qualification at Greenwich Park.
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 Friday, go forward to next Tuesday's 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 11th 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."
In the team competition, Germany's Kristina Sprehe cranked up the pressure on British trio Carl Hester, Laura Bechtolsheimer and Charlotte Dujardin by setting a new Olympic grand prix record.
Sprehe, who is a part of a powerful German team alongside Helen Langehanenberg and Dorothee Schneider, scored 79.11% with Desperados to move above Hester and Bechtolsheimer, who held the top two spots overnight.
And that surpassed the previous best Olympic grand prix score of 78.20%, set by Sprehe's countrywoman Ulla Salzgeber in Athens eight years ago.