Laura Trott goes into the final two events of the women's omnium with a 12-point lead over her nearest rival, with Jason Kenny, Becky James and Katy Marchant all in the hunt for medals on track cycling's final day of Rio 2016.
Trott was second behind Australian Annette Edmondson in the 500m time trial, completing her two flying laps in 35.253 seconds to open a gap of 12 points on Belgium's Jolien d'Hoore.
With the flying lap and points race to come, Trott is in a great position to defend her omnium crown and potentially win her fourth Olympic Games gold medal.
Trott isn't Great Britain's only hope of gold on the final day of track cycling at Rio 2016, which has already seen GB win four golds and three silvers.
Kenny eased into the second round of the men's keirin, in which an overall victory would move him level with former sprint teammate Sir Chris Hoy on six gold medals.
Callum Skinner, who Kenny beat to the individual sprint gold, finished sixth in his first-round heat and was relegated in the repecharge to end his chances of a third medal.
And in the women's sprint, both James and Marchant sealed 2-0 wins in their quarter finals. James faces a semi-final battle with the Netherlands' Elis Ligtlee, who narrowly beat her to keirin gold, while Marchant faces world bronze medallist Kristina Vogel of Germany for a place in the final.