Archie Atkinson lost out on Paralympic gold after a stunning collapse in the closing moments of the men's C4 4,000m individual pursuit final.
On his Games debut, the 20-year-old, the youngest rider for Great Britain, looked set to add Paralympic gold to his world championship triumph when he easily defeated Slovakia's Jozef Metelka.
But in the last 1,000 meters, Atkinson was clearly exhausted, and he lost his balance and fell off his bike at the turn.
The Cheshire native had earlier put on a truly remarkable performance in qualifying, shattering the world record with a time of 4:17.700, five seconds faster than the previous best.
In front of a startled audience at the Paris velodrome, Atkinson had to be carried off the track when the bike smacked him in the back of the head.
Although he had defeated Metelka in the qualifying round, the Slovakian managed to win the gold by staying in the race and manoeuvring around the unconscious Atkinson in the last few meters.
Even though Atkinson did not finish the race, he was given a silver medal for making it to the final. France's Gatien le Rousseau defeated fellow countryman Kevin le Cunff to win bronze.
Jaco van Gass, who established two new world records in the men's C1-3 1,000m time trial, was likewise disappointed not to take home a medal.
Van Gass surpassed his own mark from the morning session to break the C3 record in the final, riding in 1:04.825. Van Gass had competition from riders in the C1 and C2 categories because of the Paralympic competition, and three of them rode faster in the final.