Carshalton-born Rebecca Romero has won Olympic cycling gold in the women's pursuit at the Laoshan Velodrome to becomes the first British woman to win two medals in two summer Olympic sports.
The former Twickenham rower won a silver in rowing in Athens four years ago.
The 28-year-old was over three seconds quicker than fellow Brit 33-year-old Wendy Houvenaghel, who was born in Northern Ireland but represented England in the last Commonwealth Games.
Romero told BBC1: "I can't explain it. It's not the reaction I'd imagined (to winning gold) but it's magical.
"It's been so hard, I can't explain what I had to go through. I totally believe in myself now - I did before, but that was the ultimate, facing demons and up against top opposition today.
"I knew it was in me - a week ago it wasn't. Gold medals don't come easy, that's for sure."