Griffiths appears to have joined the Baptists about 1640, and founded about 1646 a London congregation in Dunning's Alley, Bishopsgate Street Without.
[1] After the Restoration of 1660, Griffith frequently got into trouble as a conventicle preacher; and persistently declined the oath of allegiance.
His difficulty was that the terms of the oath bound him to obey laws not then in being, and future sovereigns who might be Roman Catholic.
[1] Griffith was apparently free from molestation after James II's 1687 declaration for liberty of conscience.
In 1698 his small congregation received an endowment under a trust created by Captain Pierce Johns' bequest.