Dai Greene on his hampered Olympic preparations

World 400m hurdle champion Dai Greene talks to BBC Sport's Colin Jackson about his Olympic medal hopes on the eve of the British trials, which he believes are more important than ever due to his hampered preparations.

The Welshman's Olympic training has suffered after knee surgery during the winter and Greene, one of the favourites for gold at London 2012, has so far only set the 14th fastest time in the world this year.

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You can watch Britain's Olympic trials live from Birmingham this weekend as Great Britain's athletes go head-to-head to try and secure qualification for the Olympic Games, with programmes on Saturday 23 June 16:45-18:30 BST and Sunday 24 June 17:00-19:00 on BBC Two and this website.