[3] In 1684, Montagu was appointed constable of Durham Castle and spiritual chancellor of the diocese by his uncle, Bishop Nathaniel Crew.
He represented the city of Durham in James II's parliament, but probably took no active part in it and accepted the outcome of the Glorious Revolution.
The Earl of Carlisle and Sir William Blackett considered him to be "the very man" to represent Northumberland in the election of 1695,[4] but he was returned for a second spell at Durham instead, sitting as a Whig until 1702.
Such was his wealth that he appeared on a list of subscribers to the Bank of England in 1694 shown having sufficient stock to qualify for election as a director.
[5] Montagu married twice, firstly to Elizabeth Forster, daughter and heiress of Francis Forster of Belford,[6] with whom he had a son:[7] His second wife was Sarah Rogers (died 1721), with whom he had four more children:[7] Charles Montagu died in Breda, and was buried the family vault at All Saints' church in Barnwell, Northamptonshire on 29 June 1721.