[1] He was a younger son of the physician John Lewis Petit, who died in 1780, and was educated at Newcombe's School.

Prepared for university by Samuel Parlby, he entered Queens' College, Cambridge, graduating B.A.

[1] Petit was elected Member of Parliament for Ripon in 1827, through a family connection with Lancelot Shadwell, who managed the constituency for the patron Elizabeth Sophia Lawrence.

He did not stand the 1832 election for the reformed parliament, having lost Elizabeth Lawrence's support.

[1] He died on the 13th November 1849 and is buried on the western side of Highgate Cemetery.