In 1650, the Lord Protector of England, Oliver Cromwell, wrote to the Church of Scotland and said, “I beseech you, in the bowels of Christ, think it possible that you may be mistaken,” and his colorful plea is today known as Cromwell’s rule, which advises us to be less sure than we are, no matter how sure we are! After Cromwell died, his embalmed head (shown in the photo) changed hands for nearly 200 years, and in 1960 was donated to Sidney Sussex College.

KARL PEARSON, G.M/. MORANT, THE WILKINSON HEAD OF OLIVER CROMWELL AND ITS RELATIONSHIP TO BUSTS, MASKS AND PAINTED PORTRAITS BIOMETRIKA (1934) 26(3): 1–116. ©OXFORD UNIVERSITY PRESS