Great Britain's Adam Peaty set a new 50 metres breaststroke world record at the European Championships in Berlin on Friday.
The 19-year-old from Uttoxeter, who had already bettered the championship record in the heats, clocked 26.62 seconds to lower Cameron Van der Burgh's 2009 world mark in the semi-final and then vowed he had plenty left in the tank for Saturday's final.
"I didn't expect this result, even if I was close to the world record at the Commonwealth Games," the City of Derby swimmer said after setting the first individual world record of the meet.
"It was not a perfect race due to my final touch, so I can still improve tomorrow."
Eighteen-year-old Molly Renshaw claimed silver in the 200m breaststroke, swimming an excellent final 50 metres to come back from fifth place and finish second in a British record 2:23.82. Denmark's Rikke Moller Pedersen won gold, with Spain's Jessica Vall Montero securing silver.
"I'm surprised I was able to make it on the last few metres," Commonwealth Games bronze medallist Renshaw said.
"A medal was not on my mind, so I'm surprised that I was able to make it on the last few metres and I was able to better my personal best after this busy season."
Stephen Milne produced a strong finish to touch in a Scottish record 7:50.64 for fourth place in the 800m freestyle, while Jemma Lowe was sixth in the 100m butterfly.
Adam Barrett swam a 51.80 PB to win his 100m butterfly semi-final and progress to the final second fastest behind Poland's Konrad Czerniak.
Georgia Davies and Fran Halsall also booked their places in Saturday's 50m backstroke final.