I have a nappy that is badly stained from the mother of all poos that Chelsea did on Saturday

I know the sun will help to get it out but at the moment there is no sun. In fact, it's raining here as I type.
If I hang it on the line & it remains overcast & drizzly, is there any hope of the stain coming out? Should I just dry it inside & put it back in the stash & hope for some sun the next time I wash it?
I've been lucky that I've never really had to worry about stains before but this one is a doozy