Chris Walker-Hebborn and Marco Loughran returned to Ponds Forge the morning after virtually booking their Olympic places as they look to add another event to their schedule at London 2012.
On Thursday the pair both got the qualifying standard in the 200 metres backstroke at the British Gas ASA National Championships, which is also the last chance for swimmers to make Team GB.
Walker-Hebborn succeeded Loughran as European junior champion in the 100m backstroke in 2008 and he qualified fastest in 54.57 seconds with the pair set to battle it out for the one spot on the team alongside Liam Tancock over two lengths.
Adam Brown heads the 50m freestyle, in which two slots are still available, with a 22.56secs blast, while 17-year-old Matthew Johnson - surely destined for a bright future - was fastest through in the 400m individual medley (4:24.63).
Siobhan-Marie O'Connor was deeply disappointed to have missed out in the 200m individual medley in London in March when Hannah Miley and Sophie Allen claimed the two spots.
The Bath ITC swimmer had competed in the event at last year's World Championships in Shanghai, finishing 13th aged just 15, weeks after being crowned European junior champion.
However, O'Connor - now 16 - has had an impressive meet in Sheffield and posted a personal best of 1:08.61 in the 100m breaststroke. Should she reduce that by a further 0.12secs in the evening, then she could book a surprise slot alongside Kate Haywood.
The tussle for the one remaining slot in the women's 200m backstroke promises to be a ding-dong battle.
World Youth Championships bronze medallist Karley Mann heads the field in 2:12.41 ahead of former European junior champion Stephanie Proud, who returned from her Florida base for a second qualification attempt after just missing out in London.