Jason Kenny equalled Sir Chris Hoy's British record of six Olympic gold medals on a sensational night in Rio.
The 28-year-old won a dramatic keirin, that twice had to be restarted because of infringements, to add to his team sprint and individual sprint victories.
Kenny has won seven medals in total - his one silver coming at the 2008 Beijing Olympics, when he finished second to Hoy in the individual sprint.
GB's track cyclists won six golds, four silvers and a bronze in the velodrome.
Kenny was cheered on by fiancee Laura Trott, who had earlier retained her omnium title to become the first British woman to win four Olympic gold medals.
- Read more: Trott and Kenny - the Olympics' golden couple
- Day-by-day guide to what's on
- Latest medal table
"I'm proud to be part of the team's Olympic success and doing my bit," said Kenny.
"It is pretty mental [matching Sir Chris Hoy]. I was there in Beijing and knew he was special and as the years have gone by I appreciated how amazing he was then.
"To do the same is amazing."
Kenny has helped Britain win the team sprint at the past three Olympics. In addition, he has won two individual sprints and now has his first keirin title.
His victory was Britain's 19th of the Rio Olympics - equalling the gold haul from Beijing - and the 49th British medal overall.
Matthijs Buchli of the Netherlands took silver and bronze went to Malaysia's Azizulhasni Awang.
Two restarts and no disqualifications
The final had to be restarted twice after issues with the positioning of the riders and the electric 'derny' bike that sets the pace in the early laps.
Kenny appeared to have overtaken the back wheel of the derny before it left the track to signal the start of the sprint for the finish line but, after a delay of several minutes, he was allowed to continue.
"How close was Jason Kenny to not contesting that final? I'd say very close given they had already fired the gun to stop the race," British Cycling head coach Iain Dyer told BBC Sport.
"Ordinarily, procedure would dictate you have stopped the race and you make a disqualification if the rider's front wheel has been adjudged to have overtaken the wheel of the derny.
"I don't want to make it sound too coercive. They had a good front view but needed a lateral view.
"You want the photo-finish view but they don't have that here. That's a major error on their part, but all of our performance analysts had a bird's eye view of it so we could see both Awang and Jason hadn't crossed the line.
"And exactly the same proved to be the case with Joachim Eilers in the next rerun. He hadn't crossed the line either. It's just playing fair really."
'I didn't realise how special he was going to be'
Six-time Olympic champion Sir Chris Hoy: "That was a test of character. You can do all the reps in the gym but it is character and it is just fantastic to see the smile on his face. It is a really special moment.
"When he came on the team before Beijing we knew he was special but I don't think we realised how special he was going to be."
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