The church of Eglwys Dewi Sant once stood alongside Howard Gardens in Tredegarville, Cardiff. It was the church for Welsh-speaking people in Cardiff.
The economic and industrial growth of Cardiff during the nineteenth century led to demands for a church in which services were in Welsh. The outcome was the creation of Eglwys Holl Saint (All Saints? Church) in Tyndall Street which opened in 1856. However, further development led to the dispersal of the Welsh community and its replacement by non-Welsh speakers, and so congregations declined. As a result the church became All Saints with services in English only. A new church hall for holding services in Welsh was subsequently opened in Howard Gardens in 1889, and a new church built next to it in 1891 on land donated by Lord Tredegar. The church was built to designs of E.M.Bruce Vaughan, a local architect.
The church was severely damaged in an air raid in 1941. The Ordnance Survey fourth-edition 25-inch map of 1942 shows the church in ruins. It was later cleared away and the site is now occupied by buildings of the University of Wales. After the war the congregation of Dewi Sant agreed to a proposed move to Saint Andrew's church, located in St Andrew's Crecent (NPRN 14283) which had closed due to declining congregations.

Sources in additon to OS mapping:
churplansonline.org.
http://parish.churchinwales.org.uk/l301/history/

David Leighton, RCAHMW, 30 January 2015