22:05London Calling: World Have Your SayLondon Calling: Bolt strikes againBBC World Service Duration: 55 minutes Tue 7th Aug 2012, 22:05 on BBC World Service OnlineReaction as Usain Bolt becomes the first ever man to defend the 200m Olympic crown - and Kenya's David Rusdisha wins the 800m in a word record time.GenresFactualFormatsDiscussion & TalkBrandLondon Calling: World Have Your Say Source: BBC Online