The Dedication is to Thomas a Beckett, Archbishop of Canterbury, who was murdered in 1170. There are, or were formerly, a number of these dedications in the area, others being at Shirenewton, Wolvesnewton, Wyesham, Ganarew and (probably) Penrhos. Such dedications doubtless had a political background reflecting the attitude of the Church in the struggle with the King which had brought about St Thomas’s death.

The present church, or part of it, is known to have been in use in 1186 when it was mentioned in the Bull of Pope Urban III. Its original construction can therefore be dated as having taken place in all probability between 1170 and 1186. There may well have been an earlier structure on the site.

Charles Heath, writing in 1800, claimed to identify Saxon features in the arches and windows, but the evidence for this is uncertain.

Some fifty years after being built, in 1233, the church was damaged by fire (as was Monnow Bridge) in the course of the Battle of Monmouth, an action in the baronial uprising against Henry III. In the following year the King authorised the Constable of St Briavels to supply thirteen oaks from the Forest of Dean to repair the damage. In the year 1256 there is an unusual reference to the fact that anchorites were living in St Thomas’s.

For the next five hundred years, or more, information about the church is sparse.

In 1479 an Indulgence was granted by the Bishop of Hereford for the repair of the church, but in 1543 John Leland wrote (of the Monnow Gate) “beyond this gate is a suburb in the diocese of Llandaff where once stood the parish church of Saint Thomas, but now only a little chapel dedicated to the saint.”

At about this time the Monmouth Cap came into prominence. There is a widespread belief that manufacture of the famous cap was centred in Overmonnow which, as a result, became known as Cappers’ Town and Saint Thomas’s as Cappers’ Church. Mr Kissack however has pointed out (a) that nowhere in the known records is Overmonnow referred to as Cappers’ Town, nor is the term used in an contemporary accounts of Monmouth.

In 1611 John Speed published a map of Monmouth, believed to be reasonably accurate, which showed St Thomas’s Church with a square castellated tower at the Western end of a small building.

For the next two hundred years or more there is little information to be had. In the general decline in church-going during the period, Monmouth lost four of its mediaeval churches and Saint Thomas’s probably came close to suffering the same fate. A contemporary picture shows a scene of neglect and decay. The church was for many years a Chapel of Ease to Saint Mary’s Parish Church, and was used for services only on Tuesday.

In 1830 Saint Thomas’s again became a separate parish and major restoration of the church was undertaken by Thomas Henry Wyatt, a prolific architect whose uncle was agent to the Duke of Beaufort at Troy House. Wyatt installed new pews and galleries made from oak grown of the Beaufort estates. Wyatt rebuilt the West front in brick and added a turret. This turret, depicted in a print of c.1850 has been described as being “curiously slavonic”.

Further extensive restoration was carried out in 1874/5 by John Pritchard an architect who had been assistant to the famous Augustus Pugin. Wyatt’s turret was replaced and the West doorway reconstructed in stone.

The vestries were added in 1887/8. The present East window dates from 1957.

In 1989-91 an extensive restoration was carried out costing £72,000, under the direction of Jonathan Price, an architect of the firm of Hook Mason of Hereford. The heating system installed in 1966 had its oil-fired boiler replaced by a gas boiler.