Sophie Wells won Great Britain's third equestrian medal of the Paralympics at Greenwich Park today.
But the 22-year-old could not emulate her fellow Paralympic debutant Natasha Baker, who landed the Grade II individual title yesterday, in taking gold.
Wells, from Newark in Nottinghamshire, had to settle for silver behind Belgium's Michele George, a Grade IV result that was reversed from the 2010 World Equestrian Games in Kentucky.
Wells, who was born with amniotic band syndrome that affects her joints, is such an outstanding dressage talent that she has also competed at non-disabled international level.
But a mistake midway through her test today on Pinocchio cost her dear as their score of 76.323% fell short of George's 77.065% aboard Rainman, with Dutch rider Frank Hosmar and Alphaville taking bronze.
Wells' display, though, tightened the British grip on team gold after they took a commanding lead into the final day of that competition.
Wells, whose test came immediately after George's, struggled to conceal her disappointment at not securing a Paralympic individual gold, although she will be a leading contender in Tuesday's freestyle to music class.
"If I hadn't had the mistake it might have been a different story," she said.
"I knew I would have to do the best test I had ever done, but the Paralympics is when everyone is at their best.
"You can't afford a mistake, but unfortunately I had one and I take complete responsibility for that.
"The other bits in the test I was really pleased with. I tried to nail every movement, but we couldn't nail one of them and that was what lost it for us.
"Maybe the fact he (Pinocchio) is so big and powerful counted against me today.
"A simple change for us is not just stopping, I really have to drive him into it. It was the tiniest miscommunication.
"You do your best, and my best today wasn't good enough.
"I am disappointed. I knew I had blown it. But I know why I lost it, rather than not knowing why I lost it. We want to win, otherwise we wouldn't be here.
"But the horse has brought me a long way and I am pleased with him. These things happen."
George returned to the arena to watch Wells' test, and she knew gold was hers once the giant electric scoreboard flashed up her rival's marks.
"I had a fantastic ride, but I had no choice," said the 37-year-old, who has paralysis in her left leg after a knee operation went wrong when the anaesthetic entered a wrong nerve.
"I had to take some risks today - it was now or never - and we've done it. For me, the word impossible does not exist."
Ireland's James Dwyer, meanwhile, took sixth place in the class, riding Orlando.
There was more British medal success in the Grade III class, where 46-year-old Deborah Criddle won silver with LJT Akilles.
It also meant that Britain had an unassailable lead in the team competition, although no official confirmation of their fifth successive Paralympic title was expected until later today.
The team of Criddle, Wells, Lee Pearson and Sophie Christiansen preserved an unbeaten Paralympic record that began in Atlanta 16 years ago.
Taunton-based Criddle, a triple Paralympic gold medallist in Athens eight years ago, was drawn first to go in an 11-rider class.
Although her test contained some mistakes, a score of 71.267% set the standard and was not overhauled until penultimate rider and defending Paralympic champion Hannelore Brenner posted 74.133% with Women of the World.
Brenner, though, struggled to cope with the pressure and she had two errors of course early in her test. One more would have meant disqualification.
But she did enough to secure gold, while Denmark's Annika Dalskov took bronze, although her 71.200% score with Aros a Fenris ran Criddle perilously close.
Reflecting on her test, Criddle said: "I took a little bit too much right bend, and I didn't have the power or strength in my right leg to contain what I had created.
"But for the mistakes I made, it was a really good score.
"It happened, and I had to move on, so it was a case of getting him moving again and getting the swing back, which we managed to do, and we did some really good work."
A brilliant day for the British riders ended with Christiansen winning gold in Grade Ia - and confirmation of the team gold.
Drawn first to go, the Berkshire-based rider set an imperious standard on Janeiro 6, scoring 82.750%.
Her latest triumph followed double gold in the Beijing Paralympic Games four years ago, a feat she has now emulated following today's team success that was officially ratified following the conclusion of today's action.
There was a superb Grade Ia silver medal for Ireland's Helen Kearney, riding Mister Cool, on 76.700%, with Singapore's Laurentoa Tan and Ruben James 2 third.
"As long as I stayed relaxed and focused on what I had done in training, I knew I could pull out an 80%-plus test," said 24-year-old Christiansen, who suffers from cerebral palsy.
"It was always going to be tough going first in the competition, but I did my best. I've worked so hard this year."
Kearney's silver medal triumph helped lift Ireland into a superb team bronze medal place, with Germany taking the silver behind Britain.