Lithuania's Ruta Meilutyte broke the 100m breaststroke world record on the planet Championship semi-finals.
The Plymouth-based 16-year-old clocked about a minute 04.thirty seconds in Barcelona, .15 secs faster compared to previous ideal time set by Jessica Sturdy in '09.
Earlier, Meilutyte had recorded 1:04.52 in being approved, the 2nd-quickest amount of time in background and a brand new European record.
Within the 200m individual medley final, Sophie Allen was seventh and fellow Briton Siobhan-Marie O'Connor eighth.
London 2012 Olympic champion Meilutyte will aim to win Lithuania's first World Titles gold medal in Tuesday's final.
"I'm going to be possess a relaxing day tomorrow and can save my energy for that final," she stated.
"My greatest goal is accomplished now and I'll provide my favorite shot within the final. Clearly, a gold medal will be a cherry on the top from the frozen treats.Inch
Her coach Jon Rudd stated: "It feels a little surreal, however I recall the sensation from the Olympic gold medal since it is type of exactly the same.
"The program was to choose the planet record tonight because we don't wish to need to bother about occasions tomorrow - only the medal.
"[Russian rival] Yuliya Efimova will push her so she'll her have to be on her behalf toes tomorrow, however i think there's more in the future.Inch
Briton O'Connor only arrived at the 200m individual medley final after Australian Emily Seebohm drawn out to be able to focus on her preferred 100m backstroke event, however the 17-year-old found herself in second place in the midway stage.
However, she faded within the other half to complete eighth inside a race that was won by Hungary's Katinka Hosszu. Olympic champion Ye Shiwen remarkably only handled in the future 4th.
"I simply need to learn to go swimming it better," stated O'Connor. "I carry on doing that - heading out too quickly - and that i certainly think I acquired a little excited by using it as being a final."
Compatriot Allen, 21, added: "I am disappointed I wasn't capable of making an individual best like Used to do within the semi-final."
"If I'd did that point again [2:10.23], I'd will be in 4th place but hopefully as it is my initial worldwide final I'm going to be better later on."
Scottish Commonwealth champion Robbie Renwick qualified using the 4th fastest duration of 1:46.95 heading in to the final from the 200m freestyle event on Tuesday and wishes to win Britain's first medal from the titles.
"I've got a good lane for tomorrow evening and will also be anyone's race so I have reached get myself inside a good position and extremely try to choose a medal," stated the 25-year-old, who'll face US star Ryan Lochte within the final.
Chris Master-Hebborn, 23, and Lauren Quigley, 20, both skipped on places within their particular 100m backstroke finals, but each go back to compete over 200m later within the week.
Within the evening's other finals, Australia's Christian Sprenger stated 100m breaststroke gold with South Africa's Cameron Van Der Burgh second and Felipe Lima of South america third.
Victory visited Sarah Sjostrom of Sweden within the 100m butterfly in front of Australia's Alicia Coutts and US Olympic champion Dana Vollmer.
Brazilian Cesar Cielo won the 50m butterfly final.
There is frustration for Britain's Ben Proud, who didn't achieve the ultimate, but might have stated bronze using the British record of 23.10 he set finally month's tests.