Ethiopia's Tirunesh Dibaba defended her Olympic 10,000m title with a dominant display as Britain's Jo Pavey and Julia Bleasdale smashed their personal bests.
Leading with 500m to go, 26-year-old Dibaba broke away from Kenya's Sally Kipyego and Vivian Cheruiyot to win in 30 minutes 20.76 seconds.
Pavey finished seventh in 30:53.20 with Bleasdale clocking 30:55.63 in eighth.
On her fourth Olympics Pavey, 38, beat her previous best by 19.10 seconds, as Bleasdale improved by 33.96 seconds.
Dibaba's triumph was her third Olympic gold after winning both the 5,000m and 10,000m in Beijing - the first female athlete to do so.
And she could match that triumph, as she plans to run again in the shorter distance in London in the final on Friday, 10 August.
After a steady first 4,000m where the pace was 74 seconds per lap, Kipyego began to drag out the race around the halfway mark.
Ethiopia's Werknesh Kidane took it on another gear around 7,600m as the leading runners slimmed down to just four with team-mate Dibaba behind Cheruiyot and Kipyego.
With three laps to go Kipyego found the front as Kidane slipped back, but it mattered little as Dibaba tore down the finishing straight for the penultimate time.
In front of a noisy crowd clearly enjoying the first day of athletics in the Olympic Stadium, the Ethiopian runner established a 30m lead down the back straight.
And she extended it further as she completed a final lap of 62 seconds to give her opposition no chance of stripping her of her crown.