Jason Kenny won his second gold at Rio 2016 - and the fifth of his Olympics career - by beating British team-mate Callum Skinner in the individual sprint.
Kenny, the London 2012 champion in this event, had already teamed up with Skinner to win team sprint gold for Britain on Thursday.
And the 28-year-old's 2-0 triumph over Skinner on Sunday night meant he joined fellow cyclist Sir Bradley Wiggins and rower Sir Steve Redgrave on five Olympic golds while his overall medal tally is now six.
He will now turn his attentions to matching the achievements of Sir Chris Hoy at Beijing 2008 by winning a third gold at the same Games when he competes in the Keirin on Tuesday.
Hoy, who won six Olympic golds during his incredible career, triumphed in the same three events in Beijing, where he beat Kenny in the sprint final.
Now Kenny can join the Scot - in Rio as a BBC television pundit - as the Briton with the most Olympic golds with victory in the Keirin.
Just one rider per nation was permitted at London 2012 and Kenny won the selection nod ahead of Hoy, who claimed his sixth Olympic gold in the Keirin before retiring.
Kenny won the Keirin world title in 2013 in Minsk, so it is not beyond him. He is Britain's only entrant in the race which begins behind a motorised Derny bike.
Kenny qualified for the sprint in an Olympic record of 9.551 seconds, dipping under the mark of 9.703secs set by Skinner earlier in Friday's qualifying session, which ranks riders for the head-to-head sprints.
And the pair, who are room-mates in the athletes' village and train together every day, successfully negotiated the rounds to set up the second all-British final in eight years.
Kenny easily rounded Skinner in the first of the best-of-three bouts.
And the Bolton rider led out the second sprint and had too much power for Skinner, to draw level with Redgrave and Wiggins, who won his fifth Olympic gold on Friday in the team pursuit.
Kenny is engaged to Laura Trott, who won her third Olympic gold on Saturday.
For Skinner, a 23-year-old from Glasgow, it was a second medal of his debut Games.
It took Britain's tally to four golds and two silvers from five events entered in the velodrome. Britain did not qualify for the sixth, the women's team sprint.
Denis Dmitriev of Russia took bronze with a 2-0 win over Matthew Glaetzer of Australia.