Rebecca Adlington was tonight aiming to create history with a second successive Olympic gold in the 800 metres freestyle to boost Britain's chances of reaching their medal target.
Adlington can become the first British swimmer to successfully defend an Olympic title this evening, while also adding to the bronze she won over 400m on Sunday.
But even if the 23-year-old was to triumph and be responsible for 66% of the home nation's medal tally, the team would still be some way short of the target of matching the six medals won in Beijing four years ago.
Adlington, who produced the fifth fastest time in the world this year in the heats and has recorded four of the top five times in 2012, said: "I just put my head down and went for it, especially after only scraping into the 400m final.
"I was like 'I am not risking that' even if I give it a little bit more than I should do, I'd rather get in safely so I just went for it and I am pleased with that time. Obviously it's going to be a battle in the final but I've just got to see what I can get."
Adlington will face some stiff competition in the final, with Denmark's Lotte Friis qualifying just 0.09 seconds slower to set up a potential repeat of last year's World Championship showdown when Adlington triumphed in a contest which came down to the last 50m.
Britain's only other medal hope on the penultimate evening in the pool is Lizzie Simmonds in the 200m backstroke, although the 21-year-old from Beverley had to endure an "horrendous" wait to see if she had made the final after finishing fifth in her semi.
"I'd resigned myself to the fact I wasn't going to make it, finishing fifth in a semi-final it's unlikely you're going to," said Simmonds, who eventually advanced as the seventh fastest qualifier.
"Tonight is going to be a completely different ball game. I'm going to be in an outside lane again but I do tend to get caught up in the middle of the pool, it tends to stress me out a little bit."