On 26 February 1383, Hanmer was appointed the sole Justice of the King's Bench.W. Betham. The baronetage of England, or The History of the English baronets 1805, p 426. The position was one of the highest to which an attorney could aspire. From 1383 through 1387, Hanmer was summoned to and sat in Parliament as one of the triers of petitions in the House of Lords. Hanmer's fellow triers included Thomas of Woodstock, Constable of England; Henry le Despenser, Bishop of Norwich; Walter Baron Fitzwalter (d. 1386); and Baron Cobham of Kent (d. 1408). Other triers of petitions included John Bokyngham, Bishop of Lincoln, and Robert de Vere, Earl of Oxford.
