Illtud the Irishman - from Gwynedd?

Llanelltyd, Gwynedd (Showing Proximity to the Camlan of Welsh Tradition)

In keeping with my idea (see previous post) that Illtud came from the Llydaw in Gwynedd, here is an interesting piece I just found online:

Llantwit's origins

The non-Welsh-speaking Archbishop of Wales quoted in J. C. Cole's letter of August 16, obviously was unaware of the true origin of "Llantwit".

I quote from Professor E G Bowen's book, The Settlements of the Celtic Saints in Wales, (published 1956) which deals with Christianity in the post-Roman period, the Dark Ages - the period when Irish missionaries entered Wales. "Before we attempt to review the south-eastern cults as a whole, there is a matter regarding Illtud's most northerly dedication at Llanelltud, which has not hitherto been fully appreciated." Prof Henry Lewis has recently pointed out that the Welsh or Brittonic form of Illtud's name is undoubtedly "Elltud" and the corresponding Irish form would be "Iltuath".

He then goes on to state that the late Sir John Rhys made the interesting observation that the use of the Irish form in South-East Wales is attested by the name "Lan-yltwyt" or " ... Iltwyt", which was the name of St. Illtud's famous monastery before it was reduced to "Llantwit".

I would point out that "wy" in Welsh is usually a diphthong and has no equivalent sound in English, as far as I know. "wyt" certainly does not rhyme with "it."

D JENKINS 

Rhyd y Gwin, Craig-Cefn-Parc, Swansea

From https://www.walesonline.co.uk/news/wales-news/friday-26-august-2005-2384913

NOTE:  I'm checking with the experts to confirm if this information is correct.