I The body from which the thirteenth-century chapter with its eleven members originated was rooted in the practices and history of pre- Norman Bangor. When the Breton Herve was appointed bishop of Bangor in 1092, he probably encountered an ancient clas church at Bangor, one of many in early medieval Wales.4 The term clas, perhaps derived from the Latin word classis,5 meaning corpus or collegium, described a community of clergy, with an abbot or bishop at its head. The term princeps or leader was the title bestowed on a ninth-century ruler of the clas at Abergele.6 The clerics in such a community were described by Gerald of Wales as claswyr.1 A clas was usually a mother church of a district and a centre of some importance, politically and ecclesiastically.8 In the law book of Gwynedd known as Llyfr Iorwerth, a tractate gave detailed descriptions as to who could and could not ask for sanctuary within a clas, its outer limits of protection, and compensa- tion paid for offences committed while in sanctuary;9 this concept of 4C. N. Johns, 'The Celtic monasteries of north Wales', Transactions of the Caernarvonshire Historical Society, 21 (1960), 15-16; the resilience of the clas to withstand the pressures of reform ushered in by conquest and the influence of reform-minded churchmen is discussed in J. Wyn Evans, 'The survival of the clas as an institution in medieval Wales: some observations on Uanbadam Fawr', in The Early Church in Wales and the West, ed. Nancy Edwards and Alan Lane (Oxbow Monograph 16, Oxford, 1992), pp. 33-40. 5R. E. Latham, Revised Medieval Latin Word List (London, 1989), p. 90; Rhigyfarch's Life of St David, ed. J. W. James (Cardiff, 1967), pp. 12, 35; Life of St David, ed. A. W Wade-Evans (London, 1923), pp. 12, 82, 93-5; J. E. Lloyd, A History of Wales from the Earliest Times to the Edwardian Conquest (3rd edn, 2 vols., London, 1939), I, 205. 6Annfalesf CambfriaeJ, ed. John Williams ab Ithel (Rolls Ser., 1860), p. 14; Brut [y Tywysogyon,or The Chronicle of the Princes], Peniarth [MS] 20 [Version], ed. Thomas Jones (Cardiff, 1952), p. 4; Brut [y Tywysogyon, or The Chronicle of the Princes], R[ed] B[ook of] H[ergest Version], ed. Thomas Jones (Cardiff, 1955), pp. 8-9. 7 Gir[aldi] Cambfrensis] Op[era], ed. J. S. Brewer, J. F. Dimock and G. F. Warner (8 vols., Rolls Ser., 1861-91), III, 153, referring specifically to early twelfth-century St David's. 8 The History [of Gruffydd ap Cynan], ed. Arthur Jones (Manchester, 1910), pp. 124-5; Historia [Gruffudd vab Kenan], ed. D. Simon Evans (Cardiff, 1977), p. 13. 9 [Llyfr] Ior[werth.A Critical Text of theVenodotian Code of Medieval Welsh Law], ed. Aled Rhys Wiliam (Cardiff, 1960), pp. 81-3; Huw Pryce, Native Law and the Church in Medieval Wales (Oxford, 1993), pp. 193-4.