Usain Bolt wins men 's four m gold to complete historic sprint double . Rudisha of Eaton breaks his own world record in the men 's 800m . David Rudisha takes gold in one minute 40.91 seconds . Rudisha , who was inspired by Coe 's exploits , had promised him something special and did not disappoint . Caster Semenya qualifies fastest for women 's 800m final .
Usain Bolt wins men 's four m gold to complete historic sprint double . Rudisha of Eaton breaks his own world record in the men 's 800m . David Rudisha takes gold in one minute 40.91 seconds . Caster Semenya qualifies fastest for women 's 800m final .