Jonathan Fox set a new world record as British performances at the Aquatics Centre boded well for medals in the evening on the first day of competition at the Paralympics.
Fox was already the holder of the S7 100 metres backstroke world record but he lowered it by 0.59 seconds to one minute 9.86 seconds.
The 21-year-old led from start to finish in his heat and was almost three seconds faster than any of his rivals into the final.
The Manchester-based swimmer turned to the scoreboard and beat the water upon realising his achievement with the crowd at the Stratford venue ecstatic.
He said: "I came to the heat looking to qualify first for the final tonight which I have obviously done. I didn't realise I had broken the world record until I looked up at the scoreboard.
"I had wanted to go under 1:10 for a very long time and this is really the competition to do it at. I'm very happy."
Fox described the crowd as "awesome" and it was notable that there were far fewer empty seats than during the Olympics.
Now, though, Fox must put that swim behind him and return in the evening to claim his first Paralympic title and go one better than his silver from Beijing.
He said: "Some people ask how I cope with the pressure. I've got my own ways, I just keep to myself and perform to my best."