In the Middle Ages, mithridate was also used as part of a regimen to ward off potential threats of plague. According to Simon Kellwaye (1593), one should "take a great Onyon, make a hole in the myddle of him, then fill the place with Mitridat or Triacle, and some leaues of Rue". Until as late as 1786, physicians in London could officially prescribe mithridate. According to historian Christopher Hill, Oliver Cromwell took a large dose of mithridate as a precaution against the plague and found it cured his acne.