How much material has been lost through the years? Now the question is of course what do I mean by material. For example, do I mean the trivial stuff such as typed office memorandums or the less trivial—the missing live broadcasts of the early Dr Who. No, let me focus on what I consider to be the most important material of all, that which may have a positive effect on the next generation— the historical and educational material that helps our children form sophisticated models of the Universe around us.