John Clarke (c.1582–1653) was born in Essex and studied medicine at Cambridge University. In 1634 he gained the post of second physician at St Bartholomew’s Hospital, London, where the famous physician William Harvey worked as first physician. During the Civil War (1642–1651) Clarke supported the Parliamentarians, and remained in London to organise medical aid for the Parliamentary army.In 1645 Clarke became President of the Royal College of Physicians, where he enjoyed increasing power and became reader in Anatomy. During his presidency, he wrote a new edition of the College’s 'Pharmacopoeia' (1650), a book giving directions for making medicines.