The 23-year-old stormed past Rebecca Turner, already qualified for both the 200m freestyle and subsequent relay after winning gold at the British Gas Championships in March, to claim the national title in Sheffield.
She clocked a time of 1:59.47minutes at the second Olympic trials at Ponds Forge to earn one of two remaining 4x200m relay spots for London 2012 – four of six were sealed in March – with Lucy Ellis in third taking the other.
Adlington cruised to selection in the 400m and 800m freestyle at the first trials to set up a defence of both of her Olympic titles and insists whether she will now swim the relay is out of her hands.
“I’d love to be part of that relay but I have got my individual races to concentrate on. I think at the Olympics they will probably swim the fastest four in the heats,” said Adlington.
“We have no choice if we are to make the final. We have made some mistakes in the 4x2 before by swimming different swimmers and resting the good swimmers but I think rightly so we put the fastest four in.
“If they want to include me in the heat then brilliant, if not I think they need to swim the fastest four so we will see what their decision is and what they are going to do with that.”
Five Olympic spots were up for grabs on the opening day in Sheffield and, while two were picked up in the 4x200m freestyle relay, Turner remains the only one to have qualified individually.
Adlington’s time in the final was 0.35 shy of the FINA A time of 1:58.33 while Caitlin McClatchey, who hit the qualifying times in March but not when it mattered most in the final, withdrew through illness.
Of the other places available – the men’s 400m freestyle and 100m breaststroke – David Carry secured the former with victory in a new personal best of 3:46.86 to join fiancée Keri Anne-Payne on the team.
Only Robbie Renwick qualified at the first trials in March however Carry, who finished second but outside the required time on that occasion, made sure he would be joining him and swimming at his third Olympics.
Welsh swimmer Ieuan Lloyd, already qualified for London 2012 in the 4x200m freestyle relay, was left for dead as he trailed home in second with an emotional Carry left lost for words.
“I’ve never been so emotional after a race before. This season more than any has been really quite tricky for me – I’ve had an injury and other things going on. So to come back to swim like that is just really incredible,” he said.
“And there was so much more caught up in it – knowing it is going to be my last Olympics, knowing my fiancée, my wife to be, is going to be there and I want to be part of that team too.
“It's just been an incredible journey this year – to compete like this at the last chance, the Olympic trials, is just incredible and at the age of 30 too. It’s a dream come true.”
Meanwhile the 100m breaststroke place opened up by injury Dan Sliwinski last week remains untaken after Richard Webb failed to hit the FINA A time on route to victory.