The sun beat down on the Olympic Stadium on Thursday but it was a bleak morning for two men's 4x400 metres relay medal contenders as Jamaica and Kenya failed to advance to the final after an injury and a collision.
Ashton Eaton continued his push towards adding Olympic decathlon gold to his recently-acquired world record but has compatriot Tree Hardee breathing hard down his neck after seven of the 10 events.
The 4x400 relay is always one of the most exciting and incident-packed events of the Games athletics programme and it lived up to its billing on Thursday.
On a relatively thin schedule for the fans it became the focus of their attention and gave them plenty to shout about.
Host nation Britain, with a rich heritage in the event, produced an impressive run in the first of two heats as the fans found their voice.
Anchor Martyn Rooney eased up on the line to allow Trinidad and Tobago to pip them in a national record of three minutes, 0.38 seconds - both teams progressing with the same time.
The bigger drama took place earlier, however, and robbed the crowd of the opportunity of seeing South African double-amputee Oscar Pistorius in action.
Pistorius had controversially been listed to run the third leg, despite the risk of rivals tripping on his carbon-fibre prosthetic "blades" in the melee of the changeover.
However, he was left a forlorn figure as second-leg runner Ofentse Mogawane collided with Kenya's Vincent Mumo Kiilu coming into the home straight, both men crashing to the floor. Mogawane was unable to continue for last year's world championship runners up.
SOUTH AFRICA APPEAL
Kiilu picked himself up but was 40 metres adrift and his team were out of it - robbing the final of the planned appearance of 800 world record holder David Rudisha.
They were later disqualified "as their runner had cut across and caused the South African runner to fall," the IAAF said in a statement.
