Hi Blarney beats me I'm afraid, but I've moved you post over to the Electronic section, hopefully you'll get a better chance of a result in there

 

Hi you have to remove the rear spoiler to remove the lamp.I would check the wiring from the body to the tailgate on the nearside first.Wires can break causing the light not to work.

 

Hi Meganeman, thank you, that is exactly what it was, the light itself was actually ok, but one of the wires had no conductivity, so I spliced in another wire from the brake light in the booth area up through the body ,through to the booth door and into the light.