Five years on from the London Olympics many of its stars are back in the city for the World Athletics Championships. Both Usain Bolt and Mo Farah will attempt to sign off with gold at the London Olympic park. In a wide-ranging podcast we hear from Ed Warner, head of the organising committee of this World Athletics Championships, Lord Coe, IAAF president, Roger Black, two time gold medalist at the World Championships and Today reporter Zoe Conway.(Image: Mo Farah and Usain Bolt. Credit: Getty Images)