St David (the patron saint of Wales) was born in Ceredigion (Cardiganshire) and was a puritanical monk who spread Christianity through Wales, Cornwall and Brittany and other parts of Romano-Britain. To do penance he used to stand up to his neck in a cold lake - rather like standing in the water off any Welsh beach in the midsummer - always described as 'bracing' by my parents (Welsh for numbingly cold).
He founded an austere monastery in what is now the smallest city in the UK called, appropriately enough, St David's - which like much of Wales is exquisitely beautiful and until recently was regarded as so remote that two pilgrimages to St David's was thought to be equivalent to one to Rome. He died in 589 and was canonised in 1120. His exploits were reported by the historian and twelfth century travel writer Giraldus Cambrensis. Apart from causing springs to appear at will (not that impressive in most parts of wet Wales to be honest) St David's outstanding feat was to cause the ground to rise during a sermon so that he could be more easily heard...well it could have happened, although that part of Wales is not generally renowned for its seismic activity.
There are at least three variations of the name 'David' in Welsh - 'Dai', 'Dafydd' and 'Dewi'. This is fortunate and necessary because apart from it being a very common name it is the Welsh custom to call the eldest son exactly the same name as the father. So my brother's name is David Jenkins, my father's name is David Jenkins, and his father's name was David Jenkins...My brother has rather put the spanner in the works by naming his son Michael, but Michael's second name is Dafydd so maybe all is not yet lost.