In the late 1800s, Westminster Abbey clergy stumbled upon a mysterious sarcophagus. The lid was decorated with an 11th-century Anglo-Saxon cross, but the base had a fourth-century Roman funeral inscription. For nearly 150 years, the tomb has baffled experts, but the abbey's consulting archaeologist may have finally figured out who was buried there, according to a new study.

Westminster's chief mason unearthed the stone sarcophagus in 1869, but when experts investigated it, they discovered that the burial had been looted earlier that century. Experts also noticed that the carved decoration on the side of the sarcophagus was stylistically Roman , with a Latin inscription that can be translated as "To the memory of Valerius Amandinus.…