The 16-year-old Lithuanian, who trains under Jon Rudd at Plymouth Leander while studying at Plymouth College, had served notice with a heat swim just 0.07 seconds off Jessica Hardy's world mark from 2009 this morning.
That was the second fastest time in history and saw Meilutyte knock 0.68secs off her own European record before she returned to the Palau Sant Jordi on Monday night to clock one minute 04.30 secs.
It is easy to forget she still has Tuesday's final to come and she said: "I'll have a relaxing day tomorrow and save all my energy for the final. My biggest aim is accomplished now and I'll give it my best shot in the final."
The teenager freely admitted the world record was more important than gold and explained: "Well, it's one of the steps, one of the dreams. Obviously, a gold medal would be a cherry on top of the ice cream."
Meilutyte would not be drawn as to whether she could go under the 1:04 mark, saying: "I don't know, honestly. It's a hard question."
Rudd's programme in the south west is clearly flourishing with Meilutyte's training partner Ben Proud breaking Mark Foster's 10-year-old 50m butterfly record last month while diver Tom Daley is also based there.
Now Meilutyte has to return to claim the world title tomorrow although she is a swimmer who always rises to the big occasion.
Rudd is on the Lithuanian coaching team in Spain and he said: "It feels a bit surreal.
"Now I remember the feeling of the Olympic gold medal because it feels kind of the same.
"The plan was to go for the record tonight because we didn't want to worry about times tomorrow night, we just want to race seven other people.
"I think a bit of rest tomorrow morning will do her good, get her head back together - she's a big-time girl and that is what we've got tomorrow evening."
Describing the teenager as "really professional and switched on", Rudd added: "If she has got a fault she is a bit of a scatterbrain but that is part of her charm and personality and I wouldn't necessarily want to change that because that is who she is.
"She is a 16-year-old kid who is swimming quick."
Meilutyte enjoyed hero status in her native Lithuania after the Games but for Rudd, being in Britain gives Meilutyte the space she needs.
He said: "I think what helps is the manicness of the Lithuanian people after the Olympic Games was diluted by her getting back to Britain and I think that really helped her.
"I think if she was training in Lithuania she would have some problems because she would be under the spotlight 24/7.
"She can walk down the street in Plymouth and maybe one in 20 people will go 'oh that's Ruta' whereas if Tom Daley walks down the street he is mobbed."
While Meilutyte was begging the question of how far she can take her event, Allen was disconsolate as she trudged away after coming seventh in the 200m individual medley.
The Bath ITC swimmer was fourth into tonight's final but she was never higher than sixth, finishing seventh in 2:11.32.
Allen said: "I'm disappointed I wasn't able to take more off my personal best like I was in the semi-final.
"If I'd done that time again it would have kept me in fourth place so I'm gutted to finish seventh."
O'Connor, originally ninth but into the final after Emily Seebohm's withdrawal, was second at halfway before fading to 2:12.03.
She said: "I just need to learn how to swim it better, I keep going out too fast.
"I think I got a bit excited with it being a final."
Katinka Hosszu of Hungary won with Olympic champion Ye Shiwen fourth.
Renwick was a ray of sunshine, his semi-final effort of 1:46.95 seeing him into tomorrow's 200m freestyle final.
The City of Glasgow swimmer said: "I'm really happy with that. Who knows what can happen tomorrow night? It's going to be a close race that's for sure."
Chris Walker-Hebborn and Lauren Quigley were both 12th in their respective 100m backstroke semis.
Elsewhere, Australian Christian Sprenger edged out Olympic champion Cameron van der Burgh in the 100m breaststroke and Cesar Cielo successfully defended his 50m butterfly title.
Sarah Sjostrom of Sweden won the 100m butterfly.