1719-95. He was the fourth born son of ten children to James Montagu of Lackham, Wiltshire, by his wife Elizabeth, daughter of Sir John Eyles of Southbroom, Bishop?s Canning, Wiltshire. His father was a cousin of the Earl of Sandwich, and Montagu was the father of Admiral Sir George Montagu and Captain James Montagu, being predeceased by the latter. A third son, Edward Montagu 1755-99, died serving with the Army at Seringapatam.
Montagu entered the Royal Naval Academy at Portsmouth in August 1733 and then served in home waters aboard the Yarmouth 70, Captain James Poole, the Dreadnought 60, Captain Henry Medley, the Chatham guardship Dragon 60, Captain Curtis Barnett, which later went out to the Mediterranean, and the Dolphin 20, Captain Lord Aubrey Beauclerk, which was also employed on that station.
On 22 December 1740 he was commissioned lieutenant, and he was present at the battle of Toulon on 11 February 1744 aboard the Buckingham 70, Captain John Towry. During the court martial into the conduct of Vice-Admiral Richard Lestock Montagu was prominent amongst those who condemned his senior officer, and under interrogation from Lestock was accused of speaking on the instruction of the Buckingham?s captain. Montagu’s response was that ‘I never ask any man’s opinion but my own. I always considered Vice-Admiral Lestock’s conduct on that day unlike an officer’s and always said so.’ He subsequently served aboard the Namur 90, Captain William Dilke, the flagship of Admiral Thomas Mathews.
On 2 March 1745 he was promoted commander, commissioning the new Hinchingbrooke 10 for service in the Downs, and on 15 January of the following year was posted captain. Having recommissioned the Rose 20, he left her in August, joining the Ambuscade 40 shortly afterwards. With this vessel he served in home waters and under Vice-Admiral George Anson at the action with De La Jonqui?re off Cape Finisterre on 3 May 1747.
Following the cessation of hostilities Montagu was employed in commissioning the new Greenwich 50 in 1748, and he joined the guardship Kent 64 at Portsmouth towards the end of the year. From the following spring he had the new Mermaid 20, sailing to South Carolina that August but by the spring of 1750 had exchanged with Captain John Campbell back into the Kent at Portsmouth where he remained for the next couple of years. In January 1753 he recommissioned the Port Mahon 20, going out to Newfoundland and New York.
In February 1755 he recommissioned the Elizabeth 64, serving off France in 1755-6 before being appointed to the French-built Monarque 74 at Portsmouth in January 1757. One of his first duties was the appalling one of having to supervise the confinement and execution of Vice-Admiral Hon John Byng aboard the Monarque on 14 March. The Monarque went out to the Mediterranean in May, and on 28 February 1758, when in company with the Montagu 60, Captain Joshua Rowley, drove the Oriflamme 50 ashore in Admiral Henry Osborn?s action with Commodore Duquesne off Cape de Gata. She returned to Spithead from Gibraltar in July.
In February 1759 Montagu commissioned the French prize Raisonnable 64 for the Navy, going out to the Leeward Islands in April. He exchanged with Captain Molyneux Shuldham into the Panther 60 in July and returned home at the end of the year. An appointment to the Terrible 74 was prematurely curtailed when she was ordered to be broken up, but he thereafter had the Newark 80 in the Grand Fleet during 1760, then in the same year commanded the Princess Amelia 80?with the flag of Rear-Admiral Phillip Durell in the Channel, and under Admiral Sir Edward Hawke in the Bay of Biscay. On 22 June 1762 he was appointed to the Magnanime 74, which had formerly been commanded so brilliantly by Captain Lord Howe, remaining with the Grand fleet.
In May 1763 he recommissioned the Dragon 74 as a guardship at Chatham and Portsmouth, retaining her for three years, and after a period of unemployment was appointed to her sister ship and Portsmouth guardship Bellona 74 in July 1769.
Having been promoted rear-admiral on 18 October 1770, Montagu was appointed the commander-in-chief in North America in 1771, sailing out to Boston in July but suffering so severely from gout of the stomach that there was some concern for his life. In 1772 he had to send home the disagreeable news of the burning of the schooner Gaspee at Providence, Rhode Island. Remaining on that station until returning to Spithead from Halifax in July 1774 with his flag aboard the Captain 70, Captain Thomas Symonds, his position allowed him to dramatically advance the careers of his young sons.
Montagu was further promoted a vice-admiral on 3 February 1776, and was appointed commander-in-chief and lieutenant-governor at Newfoundland in March, this being of some concern to Vice-Admiral Lord Howe, three months his junior in terms of seniority, who had been appointed to the more important North American station. Sailing from St. Helens in April with his flag aboard the Romney 50, Captain Elliott Salter, he chose to supplement the force relieving Quebec at some risk to Newfoundland, and on returning to London in November he made plain his concern at the affect that American privateers supported by the French was having on his station?s trade.
During 1777 Montagu?s flagship Romney was commanded by his son George in which he sailed for Newfoundland in April, and prior to his return to Newfoundland in 1778 he briefly flew his flag aboard the Europa 64, Captain Francis Parry, during the King?s review of the fleet at Spithead in May, sailing later that month in the same vessel for Newfoundland where he re-joined his son aboard the Romney. After eventually arriving at St. John?s on 25 July he detached Commodore John Evans to take the islands of St. Pierre and Miquelon on 14 September as soon as he learned that Britain was at war with France. His return to Portsmouth aboard the Europa in the late autumn saw him sit on the court martial of Admiral Hon. Augustus Keppel which considered that officer?s conduct at the Battle of Ushant on 27 July 1778. Following the trial he attended a ball hosted by Keppel?s supporters and in April 1779 he welcomed the admiral to his residence near Portsmouth at Fareham.
Montagu was promoted admiral on 8 April 1782, and in April 1783 raised his flag aboard the Triumph 74, Captain Philip Affleck, as the commander-in-chief at Portsmouth, transferring it in the following month to the Queen 98, Captain John Wainwright. He struck his flag for the last time on 22 April and thereafter retired to his house at Fareham where he died on 7 September 1795.
On 2 December 1748 he married Sophia Wroughton of Wilcot, Wiltshire and in addition to his three sons mentioned above had one daughter and an elder son, John, who became a fellow of All Souls at Oxford and died in 1818. Until 1749 he spelt his name as Mountagu. He greatly enjoyed the patronage of the Earl of Sandwich, and in 1747 he deputised for that nobleman?s brother-in-law at his election for Huntingdon prior to being elected for the borough himself in March 1748. He retained the seat until 1754 when on Sandwich?s advice he declined to stand for re-election.
Montagu was regarded as being benevolent and of great integrity but seen as intemperate, foul-mouthed and base, being prone to complaining somewhat irreverently of his wife?s bulk.