After his mother married the nonjuror bishop Jeremy Collier, the young Deacon was introduced to many of the leading Jacobite and nonjuring figures including George Hickes.
His daughter Sarah Sophia (1731–1801) married William Cartwright (1730-99), an apothecary and later a Nonjuring bishop in Deacon's church in both London and Shrewsbury.
Though he was clearly a Jacobite, Deacon gave his primary attention to creating a nonjuring church based on primitive sources.
Joining him in his efforts were Collier, Thomas Brett and Roger Laurence, all of whom participated in the Usages Controversy that divided the Nonjuring community.
The Usages party, freed from the oversight of the established church, advocated the reintroduction of four elements to the Eucharist — the invocation of the Holy Spirit, the oblation, the mixed chalice, and the prayers for the dead.
This book included a new liturgy, "The Order of the Divine Offices of the Orthodox British Church", which replaced the earlier one from 1718.