Janine Flock

Yarnold, from Sevenoaks in Kent, snatched victory on her fourth and final run with a new track record to make it back-to-back gold medals after her triumph at Sochi 2014.

Laura Deas claimed bronze as Britain won two medals in the same event for the first time at a Winter Olympics.

Yarnold went into the final day 0.10secs off the pace after complaining of feeling dizzy, but cut the deficit as overnight leader Jacqueline Lolling of Germany slipped back to third place after the third round.

The Sochi 2014 champion trailed Austria’s Janine Flock by 0.02 ahead of the final run, meaning Yarnold was the penultimate slider to take to the track and had to watch her rival’s performance.

The Briton clocked a track record of 51.46secs to take the lead in thrilling fashion and Flock floundered, relinquishing her spot on the podium to spark jubilant celebrations among a sizeable British contingent at the Olympic Sliding Centre, including Welsh racer Deas.

An emotional Yarnold, who became Britain’s most decorated Winter Olympian, said: “I’m overwhelmed and exhausted. I don’t really know how it happened.

“After the first run I wasn’t sure whether I was going to be able to finish the race because my chest infection was so bad I was struggling to breathe and I got here only with the help of my team.

“I guess four years ago, three years ago, the whole team all dared to dream that this was possible and I just went with them all and we managed it.”

With Deas finishing third behind Lolling, and Izzy Atkin having earlier secured bronze in the women’s ski slopestyle, it was the first time Britain had won three Winter Olympic medals on the same day, overtaking the record two from Chamonix in 1924.