There is indeed a whimsical contrast between the very ordinary qualities of his mind and the very extraordinary vicissitudes of his fortune.
He was the heir of a Puritan family.

His father, Sir Edward Harley, had been conspicuous among the patriots of the Long parliament, had commanded a regiment under Essex, had, after the Restoration, been an active opponent of the Court, had supported the Exclusion Bill, had harboured dissenting preachers, had frequented meetinghouses, and had made himself so obnoxious to the ruling powers that at the time of the Western Insurrection, he had been placed under arrest, and his house had been searched for arms.

When the Dutch army was marching from Torbay towards London, he and his eldest son Robert declared for the Prince of Orange and a free Parliament, raised a large body of horse, took possession of Worcester, and evinced their zeal against Popery by publicly breaking to pieces, in the High Street of that city, a piece of sculpture which to rigid precisians seemed idolatrous.

Soon after the Convention became a Parliament, Robert Harley was sent up to Westminster as member for a Cornish borough.

His conduct was such as might have been expected from his birth and education.