Beijing: Allyson Felix justified her step-up to the 400 metres with a convincing world championships victory which helped send the misfiring United States team soaring up the medals table yesterday.


United States' Allyson Felix celebrates after winning 400 metres gold yesterday. Pic/Getty Images 

Felix, the most decorated female athlete in history based around her 200m and relay expertise, clocked a blistering time of 49.26 seconds, the best in the world this year.