He was the son of Sir John St John of Bletsoe and his wife Sybil, daughter of Rhys ap Morgan.

He succeeded his father in 1525 and was knighted the following year.

[citation needed] He was High Sheriff of Bedfordshire and Buckinghamshire for 1529–30, 1534–35, and 1549–50.

He was a Member (MP) of the Parliament of England for Bedfordshire in 1529?, 1539 and 1542.

This article about a member of the parliament of England during the fifth Parliament of Henry VIII, November 1529 to April 1536 is a stub.