Celtic pagan beliefs coexisted, and even mingled, with Roman religion throughout England. According to one of the oldest Celtic beliefs, the head was a source of unique potency, almost a life force of its own, in which one's strength and wisdom were concentrated. When someone died, their head was therefore seen as a worthy offering to the gods, which could be removed and dedicated ritually. This might explain why several of the London skulls are missing jawbones. Those that survived the deceased sometimes kept fragments of bone, possibly to protect themselves from evil spirits.