Double Paralympic champion Ellie Simmonds became the first swimmer to break a world record at London's Aquatics Centre with victory in the 200m individual medley.
The 17-year-old finished in a time of 3:08.14, beating her own previous best time by over half a second.
A tearful Simmonds said: "I can't believe I've broken a world record.
"I haven't had a great week but I've been working hard on the event. I was confident but it's a big surprise."
She was edged into second by Beijing gold medallist Heather Frederiksen in the 100m freestyle earlier in the week.
Simmonds told BBC Sport: "I have great people around me. My coach and family [in Swansea] are amazing.
"I wanted to enjoy it and getting gold is great, but a world record is something else."
Fellow SM6 swimmer Natalie Jones was second, with Rhiannon Henry, from the SM13 category, third in the multi-classification event.
Simmonds' success follows a European record from six-time world champion Susie Rodgers, who won gold in the 50m butterfly on Wednesday.
Elsewhere on day six, 11-time Paralympic medallist Sasha Kindred secured victory and a London 2012 qualifying time in the men's 200m individual medley.
As with all of those attaining the desired times this week, they will still need to compete at the British International Disability Swimming Championships in Sheffield next month to be assured of a place at the Games.
Kindred told BBC Sport: "I went a bit slower in the final, but two swims under the qualifying time is great and means I should come back in the summer for my fifth Paralympics."
James Crisp (SM9) was the runner-up with Robert Welbourn (S10) collecting bronze.
Just one swimmer was in the final of the men's 150m individual medley, but 15-year-old Lyndon Longhorne set a new British record with a time of 3:02:36 and will hope to attain a qualification time at the trials on 6-8 April.