Running from 7.30pm-10pm, the coverage peaked to 1.9m at kick-off and went as low as 742,000 in the last 15 minutes.
There was a bigger audience for the athletics on BBC Two, where there was British interest with a bronze medal for Jenny Meadows in the women's 800m.
Running from 4.45pm-9pm, the World Championships brought in an average 2.4m viewers and a 15.8% share, peaking with an audience of 3.4m just before 9pm.
However, BBC One netted the biggest audience of the night with 6m viewers for 'Who Do You Think You Are?' with actor Martin Freeman, taking a 27.8% share at 9pm-10pm.
BBC Two was next in line with 'Dragon's Den' bringing it 3.2m viewers and a 14.8% share.
'Big Brother' was on at 9pm-10pm and extended its run of scoring 2m viewers, giving Channel 4 a 9% share. It was also watched by a big audience of 501,000 on Channel 4+1.
C4 also made a big dent in the 8pm-9pm time slot with 'Location Location Location' amassing 3m viewers and a 15.2% share.
Five screened Jean Claude van Damme film 'Inferno' at 9pm-10.55pm and managed an audience of 1.3m, or 6.9% of viewing.
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