Hannah Miley secured her second Team GB Olympic berth with victory in the women's 200m individual medley final at the British Swimming Championships.
Miley, who also took the 400IM title, will be joined in London by runner-up Sophie Allen, plus Rebecca Turner, Joseph Roebuck and Roberto Pavoni.
"I knew it would be a big race on my hands," Miley, 22, told BBC Sport.
"Lots of the younger girls have done personal-best times, so it was great to see Team GB so strong and pushing me."
Allen, who trains with open water world champion Keri-Anne Payne at Stockport Metro, narrowly missed out on qualifying for the Games in the women's 200m breastroke final on Monday.
"I knew it was in me and I've been training amazingly all year, but just needed to keep my nerve and it was great," said the 19-year-old.
It was the sixth time World Championship silver medallist Miley had claimed both the 200m and 400m IM titles at the British Championships, and looking to complete his fourth successive GB title was 200m butterfly specialist Michael Rock.
However, after a strong first 100 he tired rapidly, with Roebuck and Pavoni edging him into the bronze medal position and out of the Olympic qualification spots.
"It was a good swim and I knew was capable, but in the last 20 metres I could feel the guys around me and the lungs were burning - that hurt," Roebuck told BBC Sport after attaining his second Olympic place of the week.
A disappointed Rock added: "I have to hold my hands up to the great performances by the other two guys, but I have another chance in the 100m fly, so I have to re-focus and take the one shot I have."
In the women's 200m freestyle Turner produced an incredible swim, breaking her personal best by almost a second and touching home in 1:57:65.
Caitlin McClatchey was second, with Eleanor Faulker and Joanne Jackson completing the top four and most likely the 4x200m relay team in London.
"I really surprised," Turner told BBC Sport. "I only expected to make the relay and I've made the individual spot, so I'm a bit speechless to be honest."
In the evening's multi-classification races, Heather Frederiksen put aside the health problems which saw her spend the majority of the last month in hospital by winning the 100m freestyle final.
"I'm definitely pleased," said the Beijing gold medallist. "It's my fourth final of the week and my fourth Paralympic qualifying time so can't complain at that.
Frederiksen added: "I've been in hospital for the last 3 weeks and lost part of my sight in my right eye and this is the first time I've been in the water for a while, but hopefully with a good six-month block ahead I can turn my positions here into gold [at the Games]."
In the men's MC 100m freestyle final, Sean Fraser claimed gold with 11-time Paralympic medallist Matthew Walker second.
Day four also saw a few promising semi-finals and a fascinating dual will be expected between World Championship silver medallist Ellen Gandy and Jemma Lowe in Wednesday's 200m butterfly final with less than a second separating the pair.
The men's 100m freestyle should also be an interesting race with all eight qualifiers posting sub-50-second finishes.