Fachie was Paralympic champion at Tokyo 2020 and is the reigning world champion and record holder, but he and guide Matthew Rotherham were not overly impressive in qualifying and only fourth fastest.
They needed major improvement in the final and were clearly pumped up to do so – Rotherham shouting and slapping his thighs as he entered the track – and they produced a much quicker run in the final of 59.312 seconds.
But they were overhauled by Ball and his pilot Steffan Lloyd, who started slower in the finaland trailed their team-mates by half a second after 125m, but gradually reeled in Fachie and Rotherham with a time of 58.964s.
And when German pair Thomas Ulbricht and Robert Foerstemann – who had qualified quickest – could only come third in the final, it sealed a British one-two.
“It’s unbelievable,” said Welshman Ball, 33. “Waiting for your turn to go up, we knew we’d have to follow something big from Matt and Neil, that’s how it’s always gone.
“Our partnership has had time to gel, we have been trying to match them in the first 500m, that’s what we didn’t have [before]. We have been working for this a long time and it has paid off today.”
Unwin and Holl followed Ball’s gold by confirming their ascension to the top of their discipline, having also become world champions in 2023.
Lora Fachie was aiming for her third successive Paralympic title, but was comprehensively overhauled by Unwin, who also beat her world record in qualifying by nearly two seconds.
“This was the event we wanted, we set out the goal after the World Championships last year,” said Unwin, 30.
“We said pursuit is what we want. We tried something totally new coming into this, we weren’t sure it was going to work out for us. It’s just incredible.”
Holl, 24, added: “It feels so good, this is the one we have worked three years for, what it is all about.
“Every training session, every meeting, it is for Paris, about Paris, and we are so glad we could pull it off on the day.
“I burst into tears as I ran up to my parents. It matters so much to have so many family and friends here.”