daughter of William Dudley of Clopton, near Oundle, in the same county, born in the royal manor-house of Brigstock towards the close of the fifteenth century, studied at Cambridge, and was called to the bar at the Middle Temple, where he was autumn reader in 1524 and 1531. His family claimed descent from the Earls of Salisbury. His father died on 5 Sept. 1517, and on the subsequent death of his elder brother without issue Montagu succeeded to the family estates. In 1524 he was in the commission of the peace for the counties of Northampton, Huntingdon, and Rutland. A tradition that he was speaker of the House of Commons in 1523, and was then bidden by the king to procure the passing of the Subsidy Bill on pain of death if he should fail, is inauthentic, Sir Thomas More having been speaker in that year; nor is there evidence that Montagu was ever in parliament.
In 1524 he was one of the subsidy commissioners for the county, and in 1525 in the commission of gaol delivery for the castle of Northampton. He was also commissioner under the Vagrant Act and the acts against forestalling and regrating for the town of Northampton in 1527, and in 1530 commissioner for ascertaining the extent of Wolsey's possessions within the county. In 1531 he was in the commission of sewers for Huntingdon and some neighbouring counties, and the same year was called to the degree of serjeant-at-law (12 Nov.) The event was celebrated at Ely House in a feast of unusual extravagance, which lasted five days. Among the guests were the king and queen.
On the outbreak of the insurrection known as the 'Pilgrimage of Grace' Montagu acted as commissariat commissioner to the royal forces in Northamptonshire (October 1536), and in the following year was made king's Serjeant. He profited largely by the dissolution of religious houses, receiving as his share of the spoil the numerous estates held in Northamptonshire by the abbey of Bury St. Edmunds, and other church lands in that and adjacent counties. He was knighted at the creation of the Earl of Hertford and Southampton, 18 Oct. 1537, and was advanced to the chief justiceship of the king's bench, 21 Jan. 1538-9. In December 1541 he assisted the privy council in the examination of the Duchess of Norfolk, and other proceedings preliminary to the bill of attainder against Catherine Howard. From the king's bench he was transferred to the less dignified, but also less onerous, post of chief justice of the common pleas, 6 Nov. 1545. He was a member of the commission which extorted a confession from the Duke of Norfolk, 12 Jan. 1546-7 [see Howard, homas II, Earl of Surrey, and third Duke of Norfolk of the Howard house, 1473-1554], and of the council of regency appointed by Henry VIII's will to carry on the government during the minority of Edward VI. In the council he acted with the party adverse to Somerset, whose patent of protector he refused to attest (12 March 1546-7). On the other hand, he attested the patent of 24 Dec. 1547, by which the protector's authority was made terminable at the pleasure of the king, and in October 1549 he concurred in his deposition.
Montagu was a member of the commission of heresy which tried Nicholas Shaxton, 18 June 1546, and of that which confirmed Bonner's deprivation, 7 Feb. 1549-50. An important case of peculation, that of Sir William Sherington, treasurer of the mint at Bristol, came before him at Guildhall on 14 Feb. 1548-9, and ended in the condemnation of the accused to a traitor's death. On the resumption by the crown of the privileges of the merchants of the Steelyard he was appointed, 2 March 1551-2, commissioner for adjusting their equitable claims. Summoned to council at Greenwich 11 June 1553, he attended next day, was apprised of the Duke of Northumberland's scheme for altering the succession in favour of Lady Jane Grey, and required to draft the necessary clauses for insertion in the king's will. He objected that they would be void as contravening the Act of Settlement, and obtained leave to consult his colleagues. They met at Ely House, and after a day spent in conference resolved that the project was treasonable. This resolution Montagu communicated to the council on the 14th, but was answered that the sanction of parliament would be obtained and peremptorily ordered to draft the clauses. He still hesitated, but his scruples were removed by a commission under the great seal and the promise of a general pardon, and he not only drafted the clauses, but appended his signature to the will as one of its guarantors. On the accession of Mary he was committed to the Tower, 26 July, but was discharged on 6 Sept. with a fine of 1,000l. and the forfeiture of some of his estates. He was superseded on the bench by Sir Richard Morgan [q. v.]
Montagu retired to the manor of Boughton, Northamptonshire, which he had bought in 1528, where he died on 10 Feb. 1556-7. He was buried on 5 March with much pomp (including a 'hearse of wax') in the neighbouring church of St. Mary, Weekley, where an altar-tomb with his effigy and the legend
