In Carmarthenshire;  Ystrad Tywi, territory in 12th century of Rhys ap Gruffudd, Prince of Deheubarth, who founded it and was also a generous benefactor of Whitland and Strata Florida.  He was in close connection with the Angevin court and had increasingly strained relations with Henry II.  

It was founded as the abbey of the Blessed Virgin Mary and St John the Baptist by Rhys ap Gruffydd who died in 1197.  It is virtually certain that it was founded between 1184 and 1189 and that there was previously from an early date a house of Welsh canons here.   Rhys had close relations with Ranulf de Glanville, Marcher leader.  It was a daughter of St Jean, Amiens.

There were soon Welsh canons here, and abbot Iorwerth (Gervase) became bishop of St Davids in 1215 (KNOWLES).

Early 13th century building plans are extant.  It had a square-ended aisleless presbytery with solid walls dividing the transeptal chapels originally, turning to open arches with screens between the chapels later.  A tower seems to have been planned from the first  (CLAPHAM).

There was conflict early on with the abbot of Whitland.  War at the end of the 13th century meant the abbey was impoverished, so it was taken into the king’s hands in 1284.  Edward tried to get rid of the Welsh and replace them with English speakers (SMITH).

There were bad reports about the canons’ lives and general chapter sent visitors to reform the abbey in 1284 and again in 1291, when, owing to the distance from Amiens, Talley was made subject to Welbeck, but later to Halesowen (KNOWLES) – quitclaimed by Welbeck (THOMPSON).

The abbey was supported by the 2 castles of Dinefwr and Dryslwyn and members of the Braose family;  it was well endowed with granges, churches and land.  Mismanagement by abbots led to it being taken into the king’s hands again in 1381.  It was damaged in the Glyndwr rebellion (SMITH).

At the dissolution in 1536 (?) there were 8 canons (KNOWLES).  The revenue was assessed at £136;  the lands yielded little and were put in the hands of a steward;  the income from churches was nearly 4/5 of total income (THOMPSON);  the granges close by became a royal manor of Talley;  the chancel became the parish church;  a new church was