I've used Blender for 4 years, off and on, yet I've never come across this before. I've attached two images to try and make it clear. It looks like a bounding box, it's not an object I've added and I cannot find anyway to get rid of it. Wasn't there last night.
Can anyone tell me the "Kick myself" short cut to get rid of it please? As I've not the foggiest.