After the dissolution of the monasteries in the 1530’s, the Abbey was taken over as a private house by William Morgan and rebuilt using many of the original stones. He also owned all the attached estates, including Gelli Las which appears in the survey of the manor in 1634. The estate passed down through the Morgan family, and in 1707 Sir Edward Morgan’s daughters, Anne and Frances agreed to a partition of the estates. By the 1830’s another descendant, Reginald James Blewitt was in residence and he virtually rebuilt the Abbey in 1837. It was sold to Sir Clifford Cory in 1895 who lived there until his death in 1941. In 1946 the abbey became the home for the Sisters of Saint Joseph as it still is today. It isn’t known when Gelli Las was sold off from the rest of the abbey estates; it could have been when the estates were partitioned in 1707. However we do know from the Apportment of the Rent-Charge in lieu of Tithes in 1844, Gelli Las was then owned by John Lawrence. It is referred to as being ”one hundred and fifty acres, tithe free by prescription and very well known.” John Lawrence sold Gelli Las to Henry Crawshay in 1862, who in turn sold it to Alfred Colerick Pilliner in 1871. Pilliner is noted to have been a Justice of the Peace and one of the principal landowners in the district. The Holy Trinity Church in Pontnewydd, Cwmbran was said to have an oak screen dedicated to the memory of Mrs. Pilliner of Llantarnam Grange.
