He is referred to as the Irish King's Serjeant in 1338 and as Attorney General for Ireland in 1343, although the two offices are easily confused in this era, due to the lack of precision about their respective roles. He was a justice of the Court of King's Bench (Ireland) by 1347, and in 1359 briefly replaced John de Rednesse as Lord Chief Justice.
He had two powerful patrons in James Butler, 2nd Earl of Ormond, and his wife Elizabeth Darcy, who employed le Petit as her attorney. It was at their request that le Petit in 1351 received a royal pardon for killing Robert de Lynham; little is known of the circumstances of the crime.
- Ball, F. Elrington The Judges in Ireland 1221-1921 John Murray London 1926 Vol. 1 p.83
- Ball p.83
- Hart, A. R. History of the King's Serjeants-at-law in Ireland Four Courts Press Dublin 2000 p.179
- Hart p.179