The copyhold for the site of the church on Downshire Hill was purchased from the Manor of Belsize in 1812 by a group which passed this in 1817 to a trio comprising Christian minister James Curry, "speculative"[1] builder William Woods and lawyer Edward Carlisle, Woods being involved in other development, both in Hampstead and elsewhere in London.

In 1832, the copyhold was purchased by John Wilcox, an admirer of George Whitefield, with the aid of a loan from a local dissenter.

The poet John Keats, who was living nearby at the time in what is now Keats House had earlier referred to White as "the Person of Hampstead quarrelling with all the world" and a petition was organised and signed by influential local people including the then Lord of the Manor of Belsize, Lord Galloway, and Sara Coleridge.

The proposal was rejected on the grounds that the 900 capacity of the church was too small, although in 1851 1,370 attended a service with a sermon delivered by the Archbishop of Canterbury.

[3] The plot was also considered too small to rebuild a larger church which led to a new parish church being built nearby at Rosslyn Hill named St. Stephen's, with the then minister of St John's Downshire Hill, Joshua Kirkman, becoming the first vicar of St. Stephen's.

In 1916, following financial difficulties during the First World War, the freehold was bought by Mr Albert Leslie Wright, the son of Rev.

Henry Wright beginning an enduring link with the Church Missionary Society, donations to missionary societies forming the largest item of expenditure annually from the earliest church records (1872) until World War I, and various ministers involved in overseas missionary work, including Douglas Butcher (1957–1960, was Honorary Canon of Cairo cathedral and later returned to the Middle East), Douglas Paterson (1962–1965, later joined the Ruanda Mission) and Kenneth Howell (1972–1979, earlier first Bishop of Chile, Bolivia and Peru).

The chapel stands in the conservative evangelical tradition, and has passed resolutions rejecting the leadership and/or ordination of women.

[3] The church has no recessed chancel, inscribed panels (previously along with a prominent pulpit and small communion table,[3] although these are no longer present), along with a frieze of biblical text (in gold lettering).

The features are characteristic of the emphasis on preaching in evangelical Anglican churches during the period of initial construction.