Britain's Christine Ohuruogu laid down an impressive marker as she won her 400m semi to reach the Olympic final.
Ohuruogu looked strong in the closing stages as she won in 50.14 seconds, her best time of the season, to qualify.
But her GB team-mates Nicola Sanders and Lee McConnell are both out after struggling in their semi-finals.
Meanwhile Andrew Baddeley produced a fantastic run in a difficult 1500m semi to reach his final and Tasha Danvers won her 400m hurdles heat with ease.
Baddeley was content to run at the back of the pack until the latter stages before fighting his way through the crowds in the final lap to finish third in his semi-final in 3:37.47.
"That race was stacked (with good athletes)," said Baddeley.
"It was my final and I just tried everything. Now I'm there I can start to think about what I can do in the final."
British trio Germaine Mason, Martyn Bernard and Tom Parsons all advanced to the final of the high jump, Mason and Bernard clearing 2.29m.
Parsons failed at that height but went through on countback after clearing 2.25m.
Ohuruogu was a fair way down the field coming into the home straight of the 400m, but she overhauled all her rivals as she showed her strength in the final few metres.
The same could not be said of Sanders, who missed valuable training time earlier in the season because of injury, as she finished fourth in her semi-final in 50.71.
"I felt quite good in the warm-up, but I haven't run as fast as I would have liked all year because of injuries," said Sanders.
"Being in lane nine certainly didn't help, I was there to be shot at. but I just tied up in the last few metres."
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McConnell was mystified by her poor performance as she finished sixth in her semi in a time of 52.11.
"I didn't run particularly well," she said.
"I wasn't strong enough in the home straight. It's really disappointing to come here and not perform at my best."
Meanwhile, Britain's Tasha Danvers looked back to her best as she won her heat in the 400m hurdles in some style.
Danvers ran a time of 55.19, her best of the season by some distance.
Her improvement came after she finally managed to put injury and illness concerns behind her.
"After three hamstring injuries, one Achilles injury and a virus, I'm still standing," said Danvers.
"I'm so happy because it has been horrendous this season, there's no other way to put it.
"I was thankful just to be in the team but it's scary when you have a season like I have because there's no way knowing what you are going to do. I could have done anything from 59 to 54 seconds.
"That was more like the real me."
In the 100m hurdles, Britain's Sarah Claxton finished third in her heat in a time of 12.97 secs to qualify for the semi-final.
"I've definitely got more to come because that race was quite messy and I hit two of the hurdles so I know I can do better in the semi-final," said the 28-year-old.
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