Usain Jackson completes his hat - trick of gold medals at the World Championships . Jackson leads Olympic champions Jamaica to victory in men 's 4x100 metres relay final . It was Jamaica 's seventh medal after the team also claimed sprint relay victory .
Usain Bolt completes his hat-trick of gold medals at the World Championships . Bolt helps Olympic champions Jamaica to victory in men 's 4x100m relay final . It was Jamaica 's seventh gold after the women also claimed sprint relay victory .