In a back room at University College London there are 37 heads in boxes. For years no one knew who they were.

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They're mostly death masks – plaster casts of the deceased kept as mementos or references for a portrait, etc. – but some were made while the person was still alive. You can tell if someone was dead when the cast was taken by how sunken the eyes are, how gaping the mouth is, or how much eyebrow remains in the plaster after it was pulled off the person's face (more hairs = more likely dead, because a live person would complain a bit). Some are hollow, some aren't. One of them is Napoleon; one has a tag around his neck that reads "MURDERER – DECAPITATED 1840".