This occurred between December 1752 and 9th April 1753, the dates of a Codicil of a will of Christopher Portrey 2nd of Ynys Cedwyn House and the date of a prosecution which I found in National Library of Wales, Crime and Punishment. In the Codicil she was referred to as Elizabeth John, and in the prosecution she was Elizabeth Portrey, spinster (i.e. unmarried woman) of Ystradgynlais. So the new owner of Ynys Cedwyn House, Richard Awbrey, (formerly Gough) may have arranged for the name to be changed in a local court, or as part of an undiscovered agreement with Christopher Portrey 2nd. If so, there might be extant documents as yet undiscovered. However a name can be changed without reference to any legal procedure. If Elizabeth were not the daughter of Christopher Portrey II, the name change would never have been allowed, because Portrey was the name of a Squire (esquire after his name), a member of the Gentry descended from the Princes of Wales and Richard Duke of Normandy via Isabella de Clare, wife of Sir Reginald Aubrey. If Elizabeth John had been an unrelated and illegitimate daughter of an unrelated servant, Gwenllian John, she would never have been allowed to adopt the name Portrey in those days of strict class distinction. In fact, Gwenllian John was the common law wife of Christopher Portrey. The circumstantial evidence is overwhelming. Stuart Davies discovered that Elizabeth John was baptized as the illegitimate daughter of Gwenllian John. Nothing else is known about Gwenllian John except for the prosecution I discovered at the NLW Crime and Punishment archives. There appear to be no extant baptismal or burial records for Gwenllian John. They may have been lost, because records are fragmentary, or they may have been stolen or destroyed.