Katherine Grainger and Anna Watkins underlined their status as gold medal favourites by setting a new Olympic best time as they qualified for the final of the women's double scull.
The double world champions destroyed the previous mark, set by Germany in Barcelona 20 years ago, by nearly five seconds as they won their heat in six minutes 44.33 seconds.
It was a commanding performance from Grainger and Watkins, who left world bronze medallists New Zealand trailing home in second place around two lengths behind.
The British double are now unbeaten in 22 consecutive races and their victory will have laid down a marker to their nearest rivals Australia, who pushed them close in the final of last month's Munich World Cup regatta.
The Australians Kim Crow and Brooke Pratley responded by winning their heat in a time that would have also broken the previous Olympic best.
But Britain remain the crew to beat and Grainger is now one race away from finally landing the Olympic gold medal that has eluded her so painfully for 12 years.
Grainger has won three consecutive Olympic silver medals. She celebrated the first in Sydney but the third, in Beijing four years ago, left her inconsolable.
Sick of always being the bridesmaid, Grainger spent months considering retirement before eventually deciding to continue and pursue her golden dream in London.
After a successful year in the single scull, Grainger and Watkins were thrown together in a boat for the first time at a routine training session in 2010.
The chemistry was immediate and the British crew have never been beaten. If they can extend that winning run to 23 races, Grainger and Watkins, a bronze medallist from Beijing, will be Olympic champions.