Rebecca Adlington produced the fifth fastest 800 metres freestyle in the world this year as she sent out an ominous warning to her swimming rivals.
The 23-year-old is seeking to become the first Briton to successfully defend an Olympic title and her time of eight minutes 21.78 seconds has been bettered only by herself and American 15-year-old Katie Ledecky this year.
The Nova Centurion swimmer has swum four of the five top times in 2012 but anyone who thinks gold is a mere formality should take heed of Lotte Friis, just nine hundredths of a second behind.
Friis was second behind Adlington when the Briton triumphed in a final length shootout at last year's World Championships as she wrested the world crown from the Dane.
Friis, who was locked out of the medals as Adlington took bronze in the 400m earlier this week, has said she "hopes to spoil the party" and she is a real threat to Adlington's ambitions.
City of Sheffield swimmer Eleanor Faulkner was 22nd in 8:38.00.
Adam Brown failed to make it through the heats of the 50m freestyle.
As in the 100m freestyle, the 23-year-old was the only British representative and his 22.39 was only good enough for 20th.