The light is run by 3 AAA batteries and has a small sensor. The sensor picks up movement and turns the light on. This has worked pretty well mounted into the roof of the box and the camera image is improved, although it can be a bit like a disco with the light going on and off! The hedgehog seems completely unperturbed by this!
The problem with this set up is that the light is coming from above and I cannot see the hedgehog's face very well. I saw a cheap solar fairy light set in Lichfield and decided to try to use this to mount some internal illumination in the side of the box.
There are 50 little LEDs, all powered by a solar unit that has a long cable and can be set some way away from the box, which is ideal. The box is in a very shaded area and the solar panel needs to be in a bright place if it is going to be able to recharge the batteries.