Janet Evans's monument to distance freestyle has gone from the Olympic record books: in the penultimate heat, Katie Hoff (USA) and Joanne Jackson (GBR) got inside the 4:03.85 title-winning from Seoul 1988, the American taking the time to 4:03.71, with the Brit just 0.09sec behind.
The following heat saw Federica Pellegrini (ITA), world record holder, raced 1.26sec inside her best pace at 100m, 1.22sec inside it at 200m and then was off pace by 0.21sec at 300m, as Rebecca Adlington (GBR) clawed back what had been a 3m deficit.
Adlington almost got there, drawing level with 15m to go. The Italian was not to be denied and claimed the Olympic record in 4:02.19, with the Brit on a Commonwealth record of 4:02.24.
Defending champion Laure Manaudou (FRA) was the last woman through, on 4:04.93, a time that would have won the crown at any time in history barring that supreme ahead-of-its-time effort in 1988.