"This district was defined by an Order in Council, July 21st, 1855, to be all those portions of the parishes of Henllan and Llansannan, situate on the southern and eastern sides of an imaginary line commencing on the eastern boundary of Henllan, at a point in the middle of the high road leading from Felin Segrwyd, or Egryn Mill, to Groes Fawr; and thence extending towards the north-west, along the middle of the road to Llansannan, as far the boundary of the two parishes; thence again, along the middle of the same road as far as Pont Deunant, which crosses Afon Deunant; from which this stream becomes the boundary as far as the junction of the stream called Afon Ucha, which in its turn becomes the boundary until it again meets the above-mentioned boundary between the two parishes. This area is of very considerable extent, being about eight miles long by about four in its greatest width, covering an area of upwards of 8000 acres in the several townships of Uwch Caerau and Taldrach, in Henllan, and Deunant and Grugor, in Llansannan."
[From The History of the Diocese of St. Asaph , 1908-1913, Ven. D.R. Thomas]