It is located at the site of the oldest college in the United Kingdom, once believed to have been founded as Côr Tewdws c. AD 395 by the Roman Emperor Theodosius II.

According to the 18th century polymath, Iolo Morganwg, the Côr Tewdws or 'College of Theodosius' was established in the late 4th century at a place at or near Llantwit Major called Caer Worgorn by co-founders, Emperor Theodosius and Custennin Fendigaid but was later burnt to the ground by Irish pirates and abandoned.

Fitzhamon was a Norman noble, and it is thought that he attacked Glamorgam by sea c. 1080,[13] conquering it and bringing it under the power of the Marcher Lords.

During the conquest, the wooden college and church were destroyed, and its endowments were transferred to newly established Tewkesbury Abbey, Fitzhamon's personal project.

[11] Around 1400, the East monastic church was extended with side aisles, and the roof and tower were raised to their current heights.

[15] In the 16th century, during the dissolution of the monasteries, the monastic community was disbanded, and the East chapel was adopted as the parish church.

During the dissolution and the later Puritan period, the medieval grange declined, and the interior church fell into disrepair, and many of the murals and statues were destroyed.

The grounds also include a 13th-century gatehouse, a monks' pigeon-house, ruined walls in a garden area, and mounds near the vicarage.

[18] When Parliament abolished chantries during the reign of Edward VI, the Galilee chapel fell into a ruined state for many centuries.

[20] In 2006,[20] A committee was formed for the purpose of advancing the rebuilding of the chapel as a space dedicated to displaying the Celtic stones and telling the story of Christianity as it developed at the site.

[6] An initial grant of £37,500 was awarded to the project in March, 2009 by the Heritage Lottery Fund,[6] and was used to commission Davies Sutton Architects[21] to drawn up architectural plans for the renovation.

[23] In December 2010, the project was awarded a nearly £300,000 grant from the Heritage Lottery Fund for the purpose of refurbishing the chapel.

Archeological excavations were conducted simultaneously with renovations, and in November they were surprised to find 8 complete skeletons in and around the chapel.

The opening ceremony was marked by a speech and prayer from the Reverend Huw Butler, and the red ribbon was cut by Llantwit's oldest resident, 94-year-old Gladys Kilby, in the presence of the youngest member of the community, Violet, just one day old!

[7] [25] And art and music festival was also held, and the following day the chapel was rededicated at a service presided over by Dr. Barry Morgan, Archbishop of Wales; Phillip Morris, Archdeacon of Margam; Huw Butler, Rector of Llantwit Major; and John Webber, former Rector of Llantwit Major.

A sermon was preached by Phillip Morris, and that evening a Songs of Praise service was held,[7] featuring the soloist Charlotte Ellet from the Welsh National Opera.

[22] The redesign also made the site wheelchair accessible, with a permanent wooden ramp covering the steps to the entrance, and a disabled toilet located within the chapel.

On the lower floor, a space was constructed to display the Celtic stones and modern bathroom were installed, and the former sacristy building was fitted with a tea making station.

[22] The renovation of the site employed a number of local contractors and artisans, including Corinthian Stone Masonry,[27] which was responsible for working with the existing stone walls; Veon Glass designed and produced the many frameless glass windows and doors within the chapel, including the innovative windows fitted into the crumbling walls of the chapel.

The West inscription reads: +SAMSON POSUIT HANC CRUCEM + PRO ANIMA EIUS +, or, "Samson placed his cross for his soul."

[30] Its inscription reads: IN NOMINE DI SUMMI INCIPIT CRUX SALVATORIS QUAE PREPARAVIT SAMSONI ABATI PRO ANIMA SUA ET PRO ANIMA *IUTHAHELO REX ET ARTMAIL ET TECAN, or "In the name of the most high God begins the cross of the Saviour which Samson the Abbot prepared for his soul, and for the soul of Iuthahelo the King and of Artmail and of Tecan."

The proposed refurbishment would make the West chapel more accessible to the Llantwit Major community, and provide a space for meetings, workshops, performances, and exhibitions.