To stop it coming back buy some Oil of Cloves and some teachers chalk. Dip the chalk in the oil of cloves and it will soak it up. Put the chalk into a thin cloth bag or better still one made from that material that goes behind curtains so the view is obscured when the curtains are open and hang the bag where the leather is stored. The oil of cloves will kill the mould spores. Finally after many months of reading posts on this site and learning from you alll I can make a post and help someone out. Thank you all. PS.. Just beware, the clove smell is pretty strong.