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.

For the past three years Welsh sporting superstar Gareth 'Alfie' Thomas has trained rookie runners to take part in the Cardiff Half Marathon. Two years ago, it was 'Alfie's Angels' - 16 women from the Valleys village of Deri - who crossed the finish line. Last year, he supersized and got 100 Angels from all across Wales - and 97 of them successfully finished the race. This year, Alfie's playing with fire! He's changed the brand to 'Alfie's Army', and he's recruited 100 17- to 21-year-olds to the cause. It all looked good on paper, but after 16 weeks of tears, tantrums and traumas (and that's just Alfie), will any of his terrible teens even make it to the starting line? Or will Alfie be reduced to a lonely, one-man army come half marathon day?