In the first episode, the walkers set off from Devon for Bristol and have problems before they get over the first hill, for many of them this is the most exercise they have ever done.
That's not the only problem, as the group struggle with having to camp and getting along with each other. And they start to realise that they won't lose weight if they carry on tucking into mammoth meals.
Before they reach Bristol, one of the group is threatening to quit and another is told by doctors that their body can't cope with the strain of the walk.
Not all programmes are available on 4oD. Please see our FAQs.
