An Olympic record ride by Charlotte Dujardin and Valegro in their Games debut put Britain on top in the first phase of the Olympics team dressage contest on Friday, with the Germans and Dutch close behind.
And in a development that will create a buzz in U.S. political corridors, Ann Romney's horse Rafalca and rider Jan Ebeling are through to the team final - the grand prix special set for August 7.
Rafalca, who performed on Thursday, stood in 30th place with a score of 70.243 percent.
Her showing next week will determine if she and Ebeling qualify for the August 9 freestyle, the individual final.
The 15-year-old Oldenberg mare has become something of a symbol in the United States, brandished by the Democrats as evidence presidential candidate Mitt Romney and his wife are out of touch with the common American.
Romney has tried to distance himself from the competition but his wife on Thursday called herself "thrilled to death" with Rafalca's performance.
Out of the political arena and back in the dressage one, there were several strong performances at the close of the two-day grand prix contest, with three horse-rider combinations scoring north of 80 percent - a lofty mark in dressage.
Germany's Kristina Sprehe, who stands in fourth, was the first rider of the day to break the old Olympic record with a score of 79.119 percent for her poised and smooth test.
But Dujardin and Valegro, who notched up the world record score for the more demanding grand prix special test in April, blew past them by earning an Olympic record mark of 83.663 percent for a poised and assured performance.
The previous record of 78.208 percent was set by Germany's Ulla Salzgeber and horse Rusty at the Athens Olympics.
"The marks haven't been that high, so I was hoping for an 80 really," said a beaming Dujardin, who has only been competing at the top levels of international dressage for 18 months.
"My personal best before today was 81. So to come to the Olympics and smash that is a little bit crazy. But I had such fun."
Of Valegro, she said: "He's just unbelievable. To think he's only 10 and we only started grand prix last year."
Dujardin's record-breaking performance leaves Britain on an average percentage score of 79.407 percent - in good shape to vie for team gold on August 7 with a nation that has had a stranglehold on the title for four decades.
Germany has won team gold in every Olympics since Munich in 1972, when they were knocked to silver by the Soviet Union.
That a team from Britain, an also-ran nation in dressage until the past few years, could hope to rival the Germans for top spot on the podium is impressive in and of itself.
"That's one thing about runs in sport - they have to come to an end sometime. And we're sure as hell going to try and make it end here," British equestrian team head Will Connell told Reuters.
Olympic team members Dujardin, mentor and employer Carl Hester and Laura Bechtolsheimer were part of the squad that won Britain its first-ever European Championship last year.
There may be an opening for Britain in London given that Germany lost its strongest pairing, the record-breaking Totilas and rider Matthias Alexander Rath, before the Olympics when Rath came down with glandular fever.
All three women on the German team are Olympic debutants but all completed solid grand prix tests to stand just behind Britain on an average percentage score of 78.845 percent.
Helen Langehanenberg turned in the strongest German performance. Scoring 81.140 percent for a test she said she thoroughly enjoyed, despite some early tension.
"I think they look not so bad at the moment," she said of Germany's chances without Totilas. "I think we'll give our best and we'll fight until the end."
A score of 81.687 percent for world number one Adelinde Cornelissen put her into second place and leaves the Dutch team within striking distance of the Germans at 76.809 percent.
Cornelissen said she thought Parzival could do even better in the second phase of the team competition.
"In the beginning, he was still a little bit spooky and a bit tense, so maybe the next test he'll feel more at ease from the beginning and then we can score even higher," said the world's top-ranked dressage rider.
"I hope. I have to. I have to beat the English, right?"
(Reporting by Sarah Edmonds; For all the latest Olympic news go to http://www.reuters.com/london-olympics-2012)