Baking normals not going to plan

Link to .blend file -
Screenshot of results -

Hi Guys,

I am trying to bake my high poly model to a normal map to be used on a lower poly model. However, as you can see from the screenshot it’s only baking a tiny portion of it to the normal map.

I have ensured that my low poly target is in the same location as the source and also very slightly larger so no faces are intersecting with the source. Can anyone take a look at the .blend and see what is wrong?