He was a nephew of Admiral Henry D'Esterre Darby who served with Lord Nelson at the Battle of the Nile, and it was in recognition of this family connection that John was given his middle name.

The well-known gospel tract "How the Lost Sheep was Saved"[4] gives his personal account of a visit he paid to a dying shepherd boy in this area, painting a vivid picture of what his work among the poor people involved.

However, the conversions ended when William Magee, the Anglican Archbishop of Dublin, ruled that converts were obliged to swear allegiance to George IV as the rightful king of Ireland.

During this time (1827–28) he joined an interdenominational meeting of believers (including Anthony Norris Groves, Edward Cronin, J. G. Bellett, and Francis Hutchinson) who met to "break bread" together in Dublin as a symbol of their unity in Christ.

[9] Darby said: "For my own part, I soberly think Article XVII to be as wise, perhaps I might say the wisest and best condensed human statement of the view it contains that I am acquainted with.

I believe that predestination to life is the eternal purpose of God, by which, before the foundations of the world were laid, He firmly decreed, by His counsel secret to us, to deliver from curse and destruction those whom He had chosen in Christ out of the human race, and to bring them, through Christ, as vessels made to honour, to eternal salvation.

America did not embrace Darby's ecclesiology as it did his eschatology, which is still being propagated (in various forms) at such places as Dallas Theological Seminary, and by authors and preachers such as Hal Lindsey and John Hagee.

He worked mostly in New England, Ontario, and the Great Lakes region, but took one extended journey from Toronto to Sydney by way of San Francisco, Hawaii, and New Zealand.

Charles Henry Mackintosh, 1820–1896, with his popular style spread Darby's teachings to humbler elements in society and may be regarded as the journalist of the Brethren Movement.

In the early twentieth century, the Brethren's teachings, through Margaret E. Barber, greatly influenced the Little Flock or Church Assembly Hall of Watchman Nee and Witness Lee.

[18] Darby has been credited with originating the pre-tribulational rapture theory wherein Christ will suddenly remove His bride, the Church, from this world to its heavenly destiny before the judgments of the tribulation.

[20] His main criticism was that Darby and the Plymouth Brethren rejected the vicarious purpose of Christ's obedience as well as imputed righteousness.

[21] James Grant wrote: "With the deadly heresies entertained and taught by the Plymouth Brethren, in relation to some of the most momentous of all the doctrines of the Gospel, and to which I have adverted at some length, I feel assured that my readers will not be surprised at any other views, however unscriptural and pernicious they may be, which the Darbyites have embraced and zealously seek to propagate"[22]