As one of the four members of the so-called Whig Junto, Montagu played a major role in English politics under the reigns of King William III and Queen Anne.

[2] In 1685, Montagu's verses on the death of King Charles II made such an impression on the Earl of Dorset that he was invited to town and introduced to other entertainments.

He became flustered in the middle of his speech, and upon recovering himself, observed "how reasonable it was to allow counsel to men called as criminals before a court of justice, when it appeared how much the presence of that assembly could disconcert one of their own body".

In 1694 he became Chancellor of the Exchequer, in reward for devising the establishment of the Bank of England, the plan which had been proposed by William Paterson three years before but not acted upon.

John Macky relates a short description of the circumstances leading up to Charles, Lord Halifax's impeachment, in the Secret Service Papers published by his son in 1733.

The Deficiency of Parliamentary Funds, and the growing Debts of the Nation, by the great Interest of Paper Credit, laid him but too much open to these Attacks, he having the whole Administration of the Revenue.

On the accession of Queen Anne, Montagu was dismissed from the Council, and in the first Parliament of her reign was again attacked by the Commons, and again escaped by the protection of the Lords.

At the accession of George I, he was made Viscount Sunbury and Earl of Halifax, with remainder to heirs male, a Knight of the Garter, and First Lord of the Treasury, with a grant to his nephew of the reversion of the Auditorship of the Exchequer.

[6] Alexander Pope commemorated the Earl's death in his unpublished poem "Farewell to London in the Year 1715": The love of arts lies cold and dead In Halifax's urn, And not one Muse of all he fed Has yet the grace to mourn.