Natasha Baker proved a class apart on her Paralympics debut at Greenwich Park.
The 22-year-old, from Uxbridge in Middlesex, posted comfortably the highest dressage score during Thursday morning's opening session in Grade II of the team competition.
Although Baker is riding only as an individual, her score of 76.095% aboard Cabral proved ideal preparation for her Games campaign.
She will contest individual medals on Saturday and next Monday, when she hopes to repeat her double European gold from last year.
"That was the best experience of my entire life," Baker said. "I woke up this morning and I was fine, but on the bus here I was thinking 'this is actually happening' and reality sunk in a little bit.
"I knew that I had to be calm, cool and collected and get the horse through the test, but he was so good - I am so proud of him. He coped so well with it. We came back with two gold medals from the Europeans in Belgium last year, so to come here with that level of expectation I was a bit nervous.
"He could have gone into the arena and really thought he didn't like it, so I had no inkling what he was going to be like. For him to do that well, I couldn't be more proud of him."
Baker, who contracted transverse myelitis (inflammation of the spine) when she was a child, is one of British dressage's rising stars and despite difficult conditions of driving rain for her test, she delivered a stylish performance as the dressage competition got under way.
No rider seriously threatened Baker's score, and she finished top of the pile after all 23 combinations completed their tests.
Germany's Britta Napel went closest, posting 72.524% on Aquilina 3, while Canadian Lauren Barwick scored 72.095% with Off to Paris, but Baker had served emphatic notice of her credentials building towards the individual events.