23.11.1795 adv Butler at Montagu's / 4.12.1795 Butler vdm at Montagu's / 24.12.1795 sup at Butler's with Montagu / 5.3.1796 Butler at Montagu's / 11.4.1796 meet Butler / 19.4.1796 Godwin calls on Butler (not in) / 20.4.1796 meet Butler & Montagu / 7.5.1796 at opera Butler / 23.9.1796 meet Butler vdm / 25.2.1797 again / 17.4.1797 again / 16.8.1798 again / 1.6.1805 again
All the entries connected with Montagu or with 'vdm' added (an abbreviation for a clergyman, like Rev) I presume were one person, while Augustus Butler is identifiable either by having been at his stepfather John King's or by Godwin having added D or Danvers. Three of the entries above (11.4.1796, 19.4.1796 and 7.5.1796) could in theory then have been either, but seem much more likely to have been the clergyman. Butler in Ireland 22.7.1800 and at Hamilton Rowan's 7.11.1803 seem likely to have been a third person (see Butler, Ireland). There are several candidates for the Rev Butler just in the DNB. George Butler 1774-1853 had just returned from a walking tour of Germany and had been senior wrangler at Cambridge, though not a contemporary of Montagu there. He wasn't then a clergyman but a law student and mathematics tutor, till he took his BD degree in 1804, but he had become fellow of Sidney Sussex College in 1794, which probably would have earned him the 'vdm', (he was in a list of subscribers in 1797 as Rev G Butler of Sidney College). His older brother Weeden Butler DNB 1772-1831 was ordained deacon in 1796 and priest in 1797; his father Weeden Butler DNB 1742-1823 was certainly a clergyman and headmaster of a school in Chelsea but 30 years older than Montagu. Samuel Butler DNB 1774-1839 of a different family but in the same line of scholarship and schoolteaching was ordained deacon in 1797 and priest in 1798. Thomas Butler (d.1839) was a contemporary of Montagu's at Cambridge and was ordained deacon in 1792 but no more info on him than that in Alum Cantab. There are about 7 other possibles in theclergydatabase but George Butler seems the most likely