So no pics sadly but he had a massive boil that had been brewing up for a while right next to his bumhole (hence the no pics!!)
Tried a hot bath to soothe things, and asked me to have a look at it, as he moved his bum cheek to the side, it just erupted of its own accord.
Was quite wonderful, just a lazy yellow swirl moving up through the water, looked like a lava lamp 
When it slowed down, put a bit of pressure on and the rest came out. Twas a thing of beauty and DH is now a lot more comfortable so everyone's happy