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 Admiral 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 Jonquière 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, 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.
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 Bellona 74 in July 1769. Having been promoted rear-admiral on 18 October 1770, he served as commander-in-chief in North America from March 1771-4 with his flag in the Captain 70, Captain Thomas Symonds, a position which allowed him to dramatically advance the careers of his young sons.
Montagu was further promoted a vice-admiral on 3 February 1776, and was commander-in-chief and lieutenant-governor at Newfoundland from 1776 until the end of 1778, taking St. Pierre and Miquelon from France in his summer campaigns, and returning to England each winter. His flagship was the Romney 50, commanded by Captain Elliott Salter during 1776, and by his son George from February 1777 and during 1778. Prior to returning to Newfoundland in 1778 Montagu 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. His return to Portsmouth 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.
Montagu was promoted admiral on 8 April 1782, and from 1783-6 was commander-in-chief at Portsmouth with his flag aboard the Queen 98, Captain John Wainwright. He 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.