St Geraint (Gerent) was the last King of Dumnonia (also called ‘King of the Welsh’) an old sub-Roman Kingdom which still covered much of the southwest. Much of his time was spent holding off the Anglo-Saxons. He received a letter from St Aldhelm of Sherbourne about the date of Easter because the British were still keeping to their own calculation as well as keeping their old tonsure. St Geraint complied with the letter. He died not much later.
Geraint’s sanctity stems from laying down his life his defence of a Christian Kingdom. This viewpoint was common, particularly among the Anglo-Saxon Kingdoms themselves.