John, 2nd Duke of Montagu officiated at the coronation of King George I in 1714 as Lord High Constable of England, was with the Duke of Marlborough on a campaign and later commanded the 1st Troop of Horse Guards and the 3rd Regiment of Horse and was Master General of Ordnance. He created an armoury at Boughton, the Northamptonshire seat he had inherited from his father. Although his attempt to colonise the islands of St. Vincent and St. Kitts, which he had been granted by King George I, proved disastrous, and he lost some £40,000 in the attempt, his interest in the sugar trade was sound. A flattering image of him was painted by the antiquary the Rev. William Stukeley (1687-1765) in his memoirs; he describes the Duke as showing '...modesty, mercy, humanity, openness, loyalty and courage'.
He shared Stukeley's antiquarian interest in Gothic architecture. John Cornforth in his chapter 'Boughton: Impressions and People' in T. Murdoch ed, Boughton House, The English Versailles, London, 1992, p.23, notes that he undertook historicist repairs of the late 13th century Eleanor Cross at Geddington, Northamptonshire, and to Palace House, Beaulieu. The library at Boughton is decorated with the coats-of-arms of the original Knights of the Garter, Montagu having been installed as a knight of that order in 1718. The pedigree over the fireplace illustrates the descent of the Montagu and Percy families from King Edward I. He added to his father's work on the gardens, employing John Topping as 'Engineer & Surveyor of my Waterworks at Boughton' in 1723. These he put to use satisfying his sense of humour by tricking unsuspecting guests. His mother-in-law was later to write to Lord Stair that 'All my son-in-law's talents lie in things only natural in boys of fifteen and he is about two and fifty. To get people into his gardens and wet them with squirts, to invite people to his country house and put things in their beds to make them itch, and twenty such other pretty fancies' (The Duchess of Marlborough to Lord Stair, Horace Walpole, Letters, vol. 1, p.339). His greatest architectural commission was the new Montagu House, the Privy Garden, Whitehall, designed and built by Henry Flitcroft (1697-1769) between 1727 and 1732.