Only a few posts on this thread have mentioned Britannia Coconut dancers. Their website says "the custom of blackened faces are thought to reflect a pagan tradition as a disguise from the evil spirits / and part of the mining connections". It also says "the dances are known to be originated with Moorish pirates which the costume is that of what a Moorish pirate would wear." Take those statements with as much salt as you like: I suggest several handfuls. But still, is there the slightest chance of their changing from blacking up?