Double Olympic champion Rebecca Adlington booked her place in the British squad for the London Games on Sunday with a winning 400 metres freestyle time that was even quicker than her Beijing triumph four years ago.

The 23-year-old, who had admitted on the eve of the national championships that the fear of failing to make the Olympic squad was “killing” her, led from start to finish at the London Aquatics Centre, clocking four minutes 02.35 seconds.

“There is so much relief, happiness, excitement. It’s an amazing feeling,” she said. “I just started crying because it is four years of training, it’s not just since Shanghai (2011 World Championships).

“I know the younger guys have got the next Olympics but London has always been my target and to know I am now going is the best thing in the world.”

Olympic bronze medallist Jo Jackson held off Eleanor Faulkner for second place.

As well as Adlington and Jackson, Ellen Gandy set a British record as she and Fran Halsall made the Olympic team in the 100m butterfly.

Jackson appeared on the brink of overtaking her friend as the queen of distance swimming in Britain, but illness and asthma struck and it was not until this time last year that she began to recover.

“That last 50 metres I put everything into and it kind of makes the lows a little bit easier,” she said. “When things haven’t been going so well, it puts it all into perspective. I’ve just got a smile on my face, which hasn’t happened for a while.”

In the men’s events, Daniel Sliwinski and 17-year-old world junior champion Craig Benson qualified in the 100m breaststroke.

Ellen Gandy broke the British record in the 100 metres butterfly as she booked her place in the Olympics.

Gandy made up ground on Fran Halsall in the final metres to touch in 57.25 seconds. Halsall was second in 57.56, with both women’s times inside that required by British Swimming to qualify for the GB team.