The second part of a two-part series in which Gareth 'Alfie' Thomas trains 100 teenagers to run the Cardiff Half Marathon. Motivating a large group young people to run 13.5 miles is a challenge in itself, but Alfie has had to support many of the teenagers through their own individual challenges, including runners like Liam who has dwarfism, a condition which presents significant challenges in training for an event like this.