Reaction and analysis from the opening session of the World Athletics Championships in London, where world record holder Usain Bolt began his bid for a 12th gold medal in what is expected to be his final appearance at a major championship.Elsewhere on the track Britain's defending champion Mo Farah was running for gold in the 10,000m, while double-European champion Laura Muir was also in action in the heats of 1500m.Expert analysis is provided by eight-time world champion Michael Johnson, while a stellar commentary team is led by 1500m world gold medallist Steve Cram along with marathon world record holder Paula Radcliffe, Olympic heptathlon champion Denise Lewis, double 110m hurdles world champion Colin Jackson, former javelin world record holder Steve Backley, Brendan Foster and Andrew Cotter.