Former world champion Gemma Spofforth was impressive as she eased through the heats of the 100 metres backstroke on the second morning of the Olympic trials at the Aquatics Centre.
Spofforth safely negotiated the two-length race in which she was alongside European silver medallist Lizzie Simmonds. The Florida-based swimmer touched in one minute 00.82 seconds with Simmonds the second Briton home 0.62secs behind, the pair sandwiching Germany's Jenny Mensing.
As the championships are a test event for the summer, foreign swimmers are eligible to compete but they have separate finals. Spofforth said: "I wasn't actually excited or nervous until [Saturday] night when I really felt it.
"I was shaking a little bit and I was excited that I was nervous because I've been a little flat coming into it. So it's a nice feeling to get the first race out of the way."
Both women admitted the curved roof and lighting inside the Aquatics Centre was not initially conducive to following a straight line.
Florida Gator Spofforth described it as "confusing" while Simmonds added: "Every roof is different - that sounds really, really boring. It sounds as if I'm going to start discussing my conservatory!"
She added: "It wasn't really on my mind, I was just more like get going, have a race and blow the cobwebs away. It becomes a personal thing, how it makes you feel to swim.
"For me it was about getting in there, doing a decent first 50 but then knowing you have a hell of a lot more to come and just relaxing with control, still with speed obviously."
Robert Bale led the Britons into Sunday night's 200m freestyle semis in 1:48.41 ahead of highly-rated teenager Ieuan Lloyd and Robbie Renwick.
Commonwealth bronze medallist Kate Haywood, who moved to Australia last year to train alongside the likes of triple Olympic champion Leisel Jones, was the fastest Briton in the 100m breaststroke heats in 1:08.83.