Samuel Pepys. Portrait of Samuel Pepys (1633- 1703), English administrator and diarist. Pepys was the President of the Royal Society when Newton published Principia in 1687; Pepys' name appears on the title page. As a senior government official Pepys was influential in building up England's navy to make his country a military superpower. Pepys is better known for his diary. This contains accounts of the major events of the time as well as details of everyday life. Written in a shorthand code, the diary was deciphered in 1825 and has been widely read since. Portrait of Pepys in 1666. Pepys, being a keen musician, is shown holding one of his own compositions.