How to remove a texture paint material slot?

I accidentally added a second slot which i didnt want and it has caused problems. I have exactly the same issue as described at this link (https://cgcookie.com/questions/1705-blender-2-8-how-to-delete-a-texture-slot-in-texture-paint-mode?ltid=1705)

However, the suggested action doesn’t work. Unlinking the datablock in the left window, saving and reloading the file just isnt working. It’s always still there after. Why can’t there just be a “remove” button as if it was a texture slot!!!?