William Clarke was an apothecary who provided lodgings for a young Isaac Newton whilst he attended King's School in Grantham. William was baptised on April 23, 1609. According to his will, he had a brother Joseph, but little else is known about his early life. William Clarke married twice, first to an unknown woman who bore him two children - Joseph and William. His second marriage was to Katherine Babington, widow, who was from the same line as Anthony Babington. Katherine had several children from a previous marriage to Edward Storer, including daughters Katherine and Anne as well as sons Edward and Arthur Storer. Together, Katherine and William had two more children named John and Martha. All of his sons except John followed him into the apothecary trade. During the English Civil War, William sided with the parliamentarians. The town of Grantham was captured by Royalists on 23 March 1643 and on April 11 he was indicted for high treason. On 11 May 1643, however the town was recaptured by Oliver Cromwell and Clarke was released. Following the war William attained wealth and landholdings, but lost much of his fortune following the restoration.