Because of the characteristic round shape of its churchyard, the cathedral is thought to be on the site of an earlier Celtic church, of which no trace remains.

A new church, dedicated to St. John, was built on the orders of Bernard de Neufmarché, the Norman knight who conquered the kingdom of Brycheiniog in 1093.

Bernard de Neufmarché also endowed the priory with lands, rights and tithes from the surrounding area, and, after his death, it passed to the Earls of Hereford, so giving it greater prosperity.

Charles Lumley (1824–1858), awarded the Victoria Cross during the Crimean War, was buried in the cathedral churchyard.

The present Dean is Paul Shackerley, who was appointed in September 2014, in succession to Geoffrey Marshall who retired earlier that year.