Georgia Davies set out a statement of intent for Glasgow 2018, breaking the European Record in the 50m backstroke heats.
The 28 year old clocked a time of 27.21, shaving almost 0.3 off her personal best and the British Record.
In an event that also saw Kathleen Dawson and Cassie Wild in a position to progress to the semis this evening, it was Dawson that secured the final British spot, with only two swimmers from each nation allowed to qualify.
Siobhan-Marie O'Connor swam a season's best performance to secure her place in the 100m breaststroke semis, with Imogen Clark also pulling out her best performance of the year to go forward to tonight's semi-finals. Sarah Vasey finished joint 15th overall and Chloe Tutton was 23rd fastest.
The Hungarian squad pulled out four of the fastest five results in the 200m butterfly, but due to the two limit on nations this meant James Guy moved from sixth to fourth fastest qualifier going through to tonight's next round. Jacob Peters, fresh from his European Juniors competition, came 24th.
Duncan Scott also secured a semi-final place in the 100m freestyle event, qualifying seventh in a huge field of 83 competitors. Craig McLean, David Cumberlidge and Calum Jarvis finished the preliminaries in 37th, 42nd and 47th respectively.
Scott said: “I need to look back at what my race was like then really just focus on myself and then I’ll see what happens in the next race.
“My preparation has been going well – it’s been fortunate that the holding camp was in Stirling so I didn’t need to drive too far to get there.
“The team looks really good as well. It’s a big team, bigger than I’ve ever been a part of, but we are quite a close knit group which is good.”
In the 4 x 200m mixed relay Cameron Kurle, Craig McLean, Kat Greenslade and Holly Hibbott fought out a close semi final, narrowly being beaten to the wall by Russia. This reflected the overall result after both heats - Russia fastest and Britain second.
In the 1500m Tom Derbyshire was the lone Brit left to battle it out, after Dan Jervis was ruled out with illness. He finished 12th overall in a heat that saw France's Damien Joly, Germany's Florian Wellbrock and Italy's Gregorio Paltrinieri make an early break that couldn't be caught.