WHY MABON, A "PREDATORY BIRD OF ELY", IS THE SERVANT OF UTHER PENDRAGON

St. Mabon's Church, Llanfabon

When I identified Uther Pendragon as Illtud, who became master of soldiers at Dinas Powys near the Ely, I was puzzled as to why the god Mabon was said to be there with him. Now I think I know why...

Llanfabon and Dinas Powys

The Rivers Taff and Ely empty right next to each other into Cardiff Bay.  Up the Taff Valley we find Llanfabon or the 'Church of Mabon.'  Nothing is known of this saint and he is probably simply a Christianzed version of the pagan god Mabon (Roman period Maponos).  [Although it is not impossible, I suppose, that Mabon, 'Divine Son', was used as an epithet for the Christ the son of God.]

From P.C. Bartram's A CLASSICAL WELSH DICTIONARY:

MABON, ST.

The presumed saint of Llanfabon, a chapel subject to Eglwysilan, near Llandaf, Morgannwg (PW 65). Maenorfabon and Maenordeilo are two townships in the civil parish of Llandeilo Fawr (WATU p.106) although Fabon (= Maenorfabon) is also said to be a township in the parish of Llangadog (Fawr) (WATU pp.68, 125). Both parishes are in Ystrad Tywi. It is apparently the proximity of Maenorfabon to Maenordeilo that suggested to Iolo Morganwg that Mabon was a brother of Teilo (Iolo MSS. p.107). There is no other support for this.

The original church at Llanfabon was medieval, and so the presence of the "saint" there much have been attested early.  COFLEIN has this listing for the church currently on the site: 

http://www.coflein.gov.uk/en/site/303261/details/st-mabons-church-llanfabon