Sprinter Jeanette Kwakye booked her place in next month's World Championships after winning the 100m at the UK Trials in Birmingham
The 2008 Olympic finalist posted 11.23 seconds, ahead of Anyika Onuora.
Dwain Chambers also made the cut, winning the men's 100m in 10.09 after Mark Lewis-Francis was disqualified.
Olympic champion Christine Ohuruogu, who has already ran the 400m qualifying time, was beaten by Perri Shakes-Drayton, who ran 51.52.
Britain can take up to three athletes in each event to the world championships in South Korea.
The top two athletes in each event at the UK Trials will guarantee their ticket to Daegu, provided they have the 'A' standard qualifying mark.
Kwakye confirmed herself as Britain's fastest woman to achieve the 'A' standard, while Liverpool Harrier Onuora's time of 11.36 met the 'B' standard but should be enough to be selected.
In the absence of teenage sprinter Jodie Williams, who has opted not to go to Daegu, Laura Turner will be expected to fill the third and final spot.
Kwakye, who has long struggled with injuries, told BBC Sport: "I feel fantastic to come back after two years. That performance was for my coach who got me back here after all those injuries.
"Fingers crossed I'll be able to emulate that at the worlds."
In the men's 100m, Chambers, who is banned from competing in the 2012 Olympics following his drugs ban, comfortably secured his place for the Worlds.
Harry Aikines-Aryeetey and Marlon Devonish achieved the 'A' standard time with both clocking 10.14 but Aikines-Aryeetey was given the second-place finish.
European silver medallist Lewis-Francis was disqualified from the race for a false start and faces an anxious wait to see if he is selected in the team.
Britain's sole track and field Olympic champion Ohuruogu, who has not run under 50 seconds since the 2008 Olympic final, could only manage third in the 400m.
A commanding performance from Shakes-Drayton won the race in 51.52, whilst Shana Cox - ineligible for the world championships - followed behind.
Ohuruogu, 27, said: "I'll honestly go home and be happy with that. I would have liked to have won it but it's a lack of training I think.
"It was good for Perri and Shana to join us to really try and make everyone run harder."
In the women's 100m hurdles, British record holder Tiffany Ofili-Porter exerted her authority on the race to ease to victory in 12.76, ahead of world hepthatlon champion Jessica Ennis.
Ennis, 25, who had thrown a personal-best in the shot put (14.25m) and won the high jump (1.89m) earlier in the day, admitted to feeling "a little bit weak by time the hurdles came around".
Nathan Woodward secured his place for the 400m hurdles in Daegu alongside European champion Dai Greene, winning in 49.66.
Second placed Richard Davenport (46.76) faces a battle with European U-23 champions Jack Green for the final third place.
Sophie Hitchon, who recently set a new British hammer record, claimed her first senior title with a fifth round throw of 67.69m.
After recording a personal best to win the women's shot put in 16.73m, Eden Francis went on to place second in the discuss (53.99m), which was won by Jade Nicholls with 56.19m.
There was disappointment for Britain's top-ranked 400m runner Michael Bingham who failed to make the final after finishing third in his heat.
European and Commonwealth 400m hurdles champion Dai Greene will contest tomorrow's 400m final alongside Martyn Rooney and Richard Buck in a bid for a place in the relay team.
The competition continues tomorrow with Phillips Idowu and Mo Farah some of the star names in action ahead of the selectors' decision on 8 August.