An angry and distraught Jody Cundy protested and boos rang around the London 2012 velodrome after the 2008 Paralympic champion was denied a restart in the men's C4/5 one-kilometre time-trial.
After Sarah Storey's triumph on day one, Cundy, another swimmer-turned-cyclist, was seeking his third Paralympic cycling title and sixth in all.
Cundy, a lower leg amputee and C4 rider, had a problem at the start and commissaires ruled he could not restart, despite coach Chris Furber's pleas, provoking an expletive-laden rant from the Briton.
Officials argued the first start was down to rider error, not an equipment failure.
Alfonso Cabello finished in a C5 world record of 1:05.947 to claim gold with world champion Jon-Allan Butterworth, who lost his left arm while serving in Iraq with the RAF in 2007, taking silver in 1:05.985, 0.038 behind the Spaniard. Bronze went to China's Ji Xiaofei.
Butterworth's time was beneath his previous best, the world record set in Los Angeles in February.
Both Britons were world champions in their respective classes entering the event, which was factored due to mixing classes, but neither came away with Paralympic gold in their home Games.
There was a happier conclusion to the day's racing for Mark Colbourne, as the 42-year-old Welshman won gold in the men's C1 3km individual pursuit.
Colbourne, who won silver in the C1-2-3 one-kilometre time-trial on day one, clocked a world record of 3:53.881 to triumph, with China's Li Zhang Yu second.