Hi Dave I can remember Glyntarrell Chapel or Capel Illtud before it was demolished around 1960-70. My cousin lives at Llanilltyd Farm around 100 yards from the old Chapel. The area of Glyn Tarrell probably refers to the valley area between the source of the River Tarrell close to Storey Arms until if flows into the River Usk at Brecon. Do you have an address where you ancestor Thomas Davies was born? I was born at a farm near Libanus and know the area well. Regards Malcolm