In 1620, the decision was made to make St John's the main parish church, which was originally just a chapel of ease.

In 1638, the vicar of St Mary's, William Erbery, was forced to resign, his curate Walter Cradock had his licence revoked, and senior members of the congregation were barred from the premises after they refused to read the Book of Sports.

These people, together with others of a similar mind, formed the core of a new congregation that, after the English Civil War and subsequent Restoration, in 1696 were granted land in Womanby Street which allowed them to build the first Trinity Church (later known as a Presbyterian chapel).

[6] By 1678, with evidence from the visit of Francis Place and later essays from the Celtic scholar Edward Lhuyd, both described St Mary's as being in ruins.

[9][10] The River Taff was diverted in 1850 (by Isambard Kingdom Brunel) to create a site to build the Cardiff Central railway station, also resulting in the creation of Westgate Street.